3040 78th Ave SE, Mercer Island, WA 98040

Office · Mercer Island · Seattle-Bellevue metro, WA

One of 34 reachable office buildings in Mercer Island. Larger than 41% of office buildings in Mercer Island (median 11,827 SF), derived from assessor records.

Usable building area
8,760 SF, King County Assessor
Lot size
34,409 SF, King County Assessor
Year built
1961, King County Assessor
Stories
1, King County Assessor
Predominant use
Post Office, King County Assessor
Assessed value
$6,538,700, per the King County Assessor (not a market appraisal)
Assessed value per usable SF
$746.43/SF, derived from assessor records
Usable area / lot
0.25, derived from assessor records
Vintage
1960s vintage
Zoning
TC, King County
County use code
Post Office/Post Service

Nearby comparable buildings

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

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Sale history and market context

MakeMe Estimate: $6.77M (estimated market value), with a likely range of $5.66M to $8.23M (half of recent verified sales in this segment landed inside that range). Based on 8 verified arm's-length comparable sales (through 2026-06-01). The county roll carries a nominal improvement value for this parcel, so the estimate leans on comparable sales and the county-confirmed building area rather than the county land and improvement split. Not an appraisal. How this estimate works.

lower confidence: 1 comparable sale within 3 miles; nearest 2.5 mi. This property type carries wider measured error; treat the estimate as a starting point.

Comparable sales used as evidence

Recorded arm's-length sales of similar buildings nearby; nearer and more recent sales rank first. Buyer and seller names are withheld. Get this data via API.

Ownership tenure is not asserted for this parcel: the most recent recorded transfer is a non-market conveyance.

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

Value over time

$0$5M$10M$15M201120142017202020232026$6.77M$6.54MCounty assessed valueMakeMe Estimate range

Dark line: county assessed value per King County tax rolls. Blue line: our estimate; dashed years are a modeled backcast built from recorded arm's-length sales in the building's segment, not estimates published at the time, and years without enough sales stay unmodeled. The shaded range is the model's measured error band; about half of verified sales in the segment land inside it. Not an appraisal. How this estimate works.

Land, site, and value history

Assessed value moved from $2,925,700 (2011) to $6,538,700 (2026), up 123% over 15 years, per county tax rolls. The 2026 roll splits $6,538,700 into $6,537,700 land and $1,000 improvements.

Taxes