600 1st Ave, Seattle, WA 98104

Office · Seattle · Seattle-Bellevue metro, WA

Imagery suggests: mid-rise office, appears multi-tenant. AI estimate from public imagery. In recent public imagery (2026-06), the building appears well maintained. AI estimate from public imagery; may be outdated.

One of 957 reachable office buildings in Seattle. Larger than 75% of office buildings in Seattle (median 20,410 SF), derived from assessor records.

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Building size: 89,355 SF, King County Assessor
Lot size: 12,769 SF, King County Assessor
Year built: 1900, King County Assessor
Stories: 6, King County Assessor
Predominant use: Office Building, King County Assessor
Assessed value: $11,776,500, per the King County Assessor (not a market appraisal)
Assessed value per building SF: $131.79/SF, derived from assessor records
Lot coverage: 700%, derived from assessor records
Vintage: pre-war vintage
Zoning: PSM 100/100-130, King County
County use code: Office Building
Construction (observed): masonry, AI estimate from public imagery
Parking (observed): none visible, AI estimate from public imagery
Frontage (observed): mid block, AI estimate from public imagery

Nearby comparable buildings

Same building type, by distance. Assessor facts only; not an opinion of value.

616 1st Ave, Seattle · 0 mi · 28,480 SF · built 1900 · assessed $192.42/SF
614 1st Ave, Seattle · 0 mi · 25,492 SF · built 1902 · assessed $163.36/SF
110 Cherry St, Seattle · 0 mi · 29,200 SF · built 1903 · assessed $162.93/SF
615 2nd Ave, Seattle · 0 mi · 87,236 SF · built 1900 · assessed $178.76/SF
605 1st Ave, Seattle · 0 mi · 56,700 SF · built 1900 · assessed $194.92/SF
100 1st Ave S, Seattle · 0 mi · 54,390 SF · built 1985 · assessed $140.10/SF

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Sale history and market context

MakeMe Estimate: $11,670,199 (estimated market value), with a likely range of $10,546,967 to $15,205,717 (half of recent verified sales in this segment landed inside that range). Based on 12 verified arm's-length comparable sales (through 2026-05-29). Not an appraisal. How this estimate works.

Last sold: 2015-12-22 for $20,500,000 (recorded arm's-length sale).

Current ownership dates to 2015 (about 11 years) per recorded transfers.

2015-12-22: $20,500,000 from Eagle Wealth Pioneer LLP to Pioneer Building Level Office LLC, rec. 20151229001210

2014-01-09: $12,343,658 from 600 Pioneer LLC to Sun Capital Corporation, rec. 20140110001033

2001-09-15: transfer from Private party to 600 Pioneer LLC (non-market transfer), rec. 20020102001438

Source: King County recorded sales extract; buyer and seller shown only when a company or organization. Individual names are withheld.

Value over time

Solid line: county appraised value per King County tax rolls. Shaded range: our modeled estimate for each year, built from recorded arm's-length sales in the building's segment; years without enough sales stay unmodeled. Dots: recorded arm's-length sales. Not an appraisal. How this estimate works.

Land, site, and value history

Assessed value moved from $7,222,000 (2011) to $11,776,500 (2026), up 63% over 15 years, per county tax rolls. The 2026 roll splits $11,776,500 into $5,746,000 land and $6,030,500 improvements.

Zoning: PSM 100/100-130 (per King County)

Lot: 12,769 sq ft

Water: Water District (per King County)

Sewer: Public (per King County)

Access: Public

Street surface: Paved

Floor and use mix: Office Building 70,776 SF; Basement, Storage 11,765 SF; Retail Store 5,814 SF; Basement, Finished 1,000 SF (county building sections)

County districts report (schools, fire, sewer, council; on kingcounty.gov)

Permit history

2019-03-12: Remodel, declared value $170,000 (Screened), permit 6716690-CN

2018-08-23: Remodel, declared value $70,000 (Screened), permit 6685214-CN

2017-05-01: Remodel, declared value $500,000 (Complete), permit 6513909

2016-07-12: Remodel, declared value $500,000 (Complete), permit 6513900

2016-07-12: Remodel, declared value $60,000 (Complete), permit 6545520

1998-04-10: Remodel, declared value $85,000 (Complete), permit 698248

Source: King County permit records (newest first).