Is the X-100 on the National Register of Historic Places?

Yes. It was listed on 20 June 2016, reference number 16000381. It is the only Eichler-related National Register listing in San Mateo County.

How big is the X-100?

The 1956 sales brochure says approximately 2,310 square feet. The 2026 MLS listing and county-derived records say 2,190. That is a 120 square foot, roughly five per cent discrepancy. The historic figure may include the carport or an interior garden; the current figure may reflect Assessor measurement or the later enclosure of the carport. We have not resolved it.

How many steel Eichlers were built?

Two. The X-100 in the San Mateo Highlands, 1956, by Jones and Emmons; and Raphael Soriano's All-Steel Builders Home in Palo Alto, 1955. Eichler also did a Jones and Emmons steel project at U.S. Gypsum's Research Village in Barrington, Illinois in 1954.

The X-100: Eichler's steel house, San Mateo Highlands, 1956

A bronze National Register of Historic Places plaque reading Eichler X-100, 1956, mounted on a plinth beside a grey screen-block wall. — “Eichler X-100, 1956, has been placed on the National Register of Historic Places by the United States Department of the Interior.” The only Eichler-related National Register listing in San Mateo County.

National Register of Historic Places Listed 20 June 2016 · Reference 16000381

Architects: A. Quincy Jones with Frederick E. Emmons, AIA
Designed: 1955
Ground broken: May 1956
Opened: 6 October 1956. Weekdays 1–6pm, weekends 10am–6pm. Admission free.
Frame: Six steel bents — 4″ H-section columns carrying 8″ I-beams. No interior wall carries load.
Roof: Steel decking, folded to act as a sunshade
Walls: Basalite concrete block
Skylights: Wascolite Skydomes, including one 32-foot span
Heating: Racon radiant, in the slab
Landscape: Douglas Baylis
Lot: 80 × 100 feet
Construction cost: Up to $125,000 — far above what it sold for

Section

Six bents, and nothing in the way.

The X-100 in section. Six bents of four-inch H-columns carry eight-inch I-beams; the roof deck is folded steel, which stiffens the span and shades the glass. Because the frame carries everything, no wall inside the house is structural — which is what let Jones and Emmons cut two planted gardens straight through the plan and run a thirty-two-foot skydome across the middle. Diagrammatic, from the published description and the 1956 brochure.

What it was for

A loss leader with a roof.

The X-100 was not a product. Eichler Network is explicit that it, and the Belluschi Life House two years later, functioned as marketing — built to draw traffic to the ordinary model homes the tract actually depended on. eichlerx-100.com puts it the same way: it was "marketed to address development's sales challenges."

Understanding that explains the house. It is not a refined production plan. It is a demonstration: here is what happens to a house when the structure stops being made of wood.

What the steel bought

Wood post-and-beam already gave Eichler an open plan. Steel gave him something else: a plan he could cut holes in. With six bents carrying the whole roof, Jones and Emmons could put two planted gardens, open to the sky, straight through the middle of the house — and run a thirty-two-foot skydome across it — without a single structural consequence. The master bedroom was partitioned by draperies and had no traditional windows at all.

And the gadgets

The X-100 was also a house of tomorrow in the literal sense, and the details are wonderful: a kitchen table that parted in the middle to reveal dual burners; a sunken shower with three showerheads and a skylight overhead; a fireplace that swivelled; reversible cabinet doors; a GE combination washer-dryer; Thermador built-ins and refrigerator-freezer; an A.O. Smith water heater; extensive Formica; Arcadia sliding glass doors; Armstrong flooring; Olean tile.

The visitors

Roughly 150,000 people over about three months. That figure appears in every source, which is exactly why it deserves a flag: it most likely originates in Eichler's own publicity and has never been independently audited. PCAD hedges it as "supposedly." We repeat it because it is the historical record, and we attribute it rather than assert it.

The press

Sunset. Life. Arts & Architecture. Popular Science. Living for Young Homemakers. Plus newsreel coverage.

The home should fulfil one's inner desire for happy, lighthearted everyday freedom.

Opened

6 Oct 1956

Free admission, seven days

Reported visitors

~150,000

Over roughly three months. Attributed, not audited.

Steel Eichlers ever built

2

This, and Soriano's in Palo Alto, 1955

NRHP reference

16000381

Listed 20 June 2016

Where the house sits: "one-half mile south of Crystal Springs Road on Skyline Boulevard," per the 1956 brochure's own directions.

Primary document

The plan, as it was drawn.

A period plan of the X-100. It is worth a minute, because it explains the photographs below better than any description — and because it quietly complicates one of the disputes about this house.

A period floor plan of the X-100 printed in black on white with the southern half tinted blue. Labelled rooms include carport, shop, garden, three bedrooms, hall, play area, utility, kitchen, dining, all-purpose, living, garden and entry, with a pool and patio to the south. — The X-100 plan. North is at the top. Period document, reproduced from the 1956 opening brochure. If you hold the original sheet we would like to credit it properly.

What it shows

A carport and a shop at the north-west, a planted garden beside them, then a wing of three bedrooms off a hall. Across the middle, a utility and plumbing core with the kitchen and dining wrapped around it. Either side of that core, the two big rooms: all-purpose west, living east. A second garden with the entry beside it, a play area opposite, and the pool and patio running the full width of the south side.

Everything the brochure promised is on it: the entry garden, the two interior gardens, the utility core, the all-purpose room, the children's play yard, the carport and the pool.

What it complicates

The plan labels three bedrooms. The 1956 brochure describes a master bedroom suite plus “three additional bedrooms” — four. The 2026 MLS says three.

We are not going to pretend this settles it. The likeliest reading is that the all-purpose room was counted as the fourth sleeping space in period marketing, which would also explain the modern listing reverting to three. That is an inference, and we would rather label it as one. The four open disputes →

Note the carport at top left. SAH Archipedia records that it has since been enclosed with an aluminium rollup door.

Inside

The frame is orange, and it is everywhere.

What the section drawing argues, these photographs simply show. Six bents of steel carry the whole roof, so the walls are free to be glass, or planting, or nothing at all.

An interior planted garden under a skylight, framed by orange-painted steel columns and a white corrugated steel roof deck, with a free-standing black cone fireplace at the centre and tropical planting all around. — Plate 1 **An interior garden, open to the sky** — this is the move the steel frame paid for. One of the Skydomes runs from here “through the core of the house to the second interior garden — a distance of 32 feet,” which the brochure claims was *“the largest Skydome ever installed in a residence.”* Landscape by Douglas Baylis.

A seating area inside the planted garden with a cone fireplace alight, orange steel columns, a low black sofa and a metal mobile on the wall behind. — Plate 2 **The same garden, lived in** — a free-standing cone fireplace stands here today. The 1956 house was reported to have a fireplace that swivelled; whether this is that fireplace, we cannot say.

A living room with two orange swivel chairs, orange steel columns and beams, a white corrugated steel ceiling, and full-height glass looking onto a kidney-shaped pool with hills beyond at dusk. — Plate 3 **Living, to the pool** — the glass runs corner to corner because no part of that wall is holding anything up. The ceiling is the underside of the folded steel roof deck.

A kitchen with pale yellow and grey cabinet fronts, a long counter, and two white freestanding islands under an orange steel beam and white corrugated ceiling. — Plate 4 **The kitchen** — sitting in the middle of the plan against the utility core, exactly where the drawing puts it. Yellow and grey fronts, a wall of built-ins, and two free-standing tables rather than a fitted island.

A close view of a white kitchen table with an electric cooktop recessed into its surface, with the pool and living room visible beyond through full-height glass. — Plate 5 **The table that cooks** — the brochure's phrase is “a cooking surface concealed under the table top,” with Thermador's Speed-Matic element, *red hot in 26 seconds*. It is still there.

A tiled shower with one overhead head and five body sprays on the wall, beside a vanity with pale yellow cabinet fronts lit by a skylight. — Plate 6 **The shower** — the 1956 brochure calls it “a sunken shower room with the sky for a ceiling.” Seventy years on the sky is still the ceiling; the fittings are now a head and five body sprays.

A bedroom enclosed by floor-to-ceiling metal chain-mail curtains with circular motifs, behind an orange steel column, with a dracaena in a planted bed beside it. — Plate 7 **A bedroom behind curtains** — the brochure is blunter than any description of it: *“A master bedroom with no windows.”* Elsewhere: “Beyond the garden is the master bedroom suite, partitioned by draperies” — Herman Miller fabrics, installed by Rodeo Interiors of Palo Alto. A startling thing to build in 1956 and a startling thing to still be looking at.

An orange lounge chair on a polished black terrazzo floor inlaid with pale circles, looking through planting to the chain-mail-curtained bedroom beyond. — Plate 8 **Circles in the floor** — the terrazzo is laid with pale discs that step through the planting.

A bedroom with white and grey walls, an orange steel beam overhead, and a sliding glass door opening onto a covered walkway. — Plate 9 **One of the three** — from the bedroom wing on the plan, opening onto the covered walk.

A study with a desk, two abstract mid-century artworks on a grey wall, an orange steel beam, and sliding glass onto a screen-block courtyard. — Plate 10 **Glass to a walled court** — screen block outside, steel inside.

The entry walk at dusk: a concrete path beside a glazed wall, a yellow front door standing open, a circular-motif metal gate and a screen-block wall with a river-stone bed. — Plate 11 **The entry garden** — first item on the brochure's room list. You can see straight through the house to the pool from the front gate.

The house at dusk from across the pool, the whole glazed wall lit from within showing the kitchen and living room, with the water reflecting the light. — Plate 12 **From the water** — the pool was on the plan from the start, not added later. This is the elevation the house was designed to have.

A wide aggregate terrace with butterfly chairs and a pool at sunset, looking west over open grassland to wooded ridges. — Plate 13 **West, from the terrace** — open land, then ridge. This is the watershed, and it is the view Eichler's own brochure was selling when it promised “spectacular vistas” and land “unspoiled by man.”

Photography of the X-100 on this page is by Sabrina Huang, reproduced with permission. Please credit accordingly if you share it. The X-100 is a private residence and is not our listing. It is documented here because it is a National Register property and a published work of architecture.

From the 1956 opening brochure

The room programme, as Eichler printed it.

Entry garden
Two interior living gardens, planted, open to the sky
Master suite, partitioned by draperies, no traditional windows
Three additional bedrooms
Two compartmented baths
All-purpose room

Utility and plumbing core
Children's play yard
Carport — since enclosed with an aluminium rollup door
Swimming pool
Approximately 2,310 sq ft of living space
Sponsors and suppliers: Thermador, Waste King, GE, Racon, A.O. Smith, Formica, Arcadia, Wascolite, Armstrong Cork, Olean, Basalite concrete block, and Herman Miller — furniture, and the drapery fabric, installed by Rodeo Interiors of Palo Alto

The brochure is on archive.org and it is the single best primary document for this house. Note that its bedroom count — a master suite plus three — does not match the current listing.

Where the record disagrees with itself

Four things about this house that are not settled.

The best-documented Eichler in San Mateo County still has four open questions in its own file. We would rather show you them than paper over them.

Square footage — 2,310 or 2,190

SAH Archipedia and the 1956 sales brochure both say approximately 2,310 square feet. The 2026 MLS and county-derived records say 2,190. That is 120 square feet, about five per cent. Plausible causes: the historic figure may have included the carport or an interior garden; the current figure may be Assessor measurement, or may reflect the carport's later enclosure. Quote whichever you need, but say which one you are quoting.

Bedrooms — settled, and it is three

This one circulated as a dispute and it should not have. We had read secondhand that the 1956 brochure described a master suite plus “three additional bedrooms,” which would make four, against the 2026 MLS listing of 3 bd / 2 ba.

We went back to the brochure text itself. It says: “The second and third bedrooms in the Eichler Homes X-100 are beyond the master bedroom, opening to the children's play yard through Arcadia sliding glass doors.” Master, second, third. Three.

So the 1956 brochure, the period plan with its three labelled bedrooms, and the modern listing all agree. There was never a discrepancy — only a misreading, and it was ours until we checked the primary document. The brochure →

First sale price — $47,000 or $60,000

Wikipedia says the house sold for $60,000. eichlerx-100.com says first owner Jesper Petersen bought it from Eichler for $47,000 in 1957. That is a 28 per cent disagreement. Both agree construction cost ran up to $125,000, so Eichler took a substantial loss either way. Separately, Eichler Network names Anna-Lise Pedersen as the 1964 purchaser and long-term steward, who kept the house close to original until her death in 2003. Whether "Petersen" and "Pedersen" are the same party, related parties or a transcription drift, we could not determine.

Current ownership — sources point opposite ways

Wikipedia says Marty Arbunich, who restored the house and directs Eichler Network, "became sole owner in 2013." An automated property-data site says the house has been owned by a private individual since May 2013 who purchased it from Arbunich and John Eng. Most likely a 2013 deed transferred the Eng interest to Arbunich and the automated parser read grantor and grantee backwards — but the way to settle that is the San Mateo County Recorder, not either website, and we have not pulled it.

On the market — status as at the date shown, verify before relying

The X-100 was listed for sale on 29 April 2026 at $4,498,000 — 3 bd / 2 ba, 2,190 sq ft, on an 8,803 sq ft lot — by Coldwell Banker, MLS ML82039557. The listing copy cites the six exposed steel I-beams, the thirty-two feet of skylights, the two private garden atriums and the National Register listing. It was covered in the local press in May 2026.

An automated valuation site simultaneously showed the house as not listed for sale, with an estimate of $4.16M–$4.45M. The listing brokerage is authoritative; the automated site was stale.

We are a Compass team and this is another brokerage's listing — we mention it because it is part of the house's public record, not as an offering. Everything above is the record as at April–May 2026. Whether it is still on the market today is a question for the MLS, and we would check it rather than trust this page. Ask us and we will look.

Talk to us

Buying or selling a house with a history?

Most Highlands Eichlers are not on the National Register — but plenty of them have a documented plan, a named architect and a first-owner story that adds real value when it is told properly. We research that before we list.

The X-100.