Portside, 403 Main: one transfer this year, a top-floor corner two-bedroom at $1,300,000 off the MLS, bought from the developer in December 1997 for $425,000 and offered for rent at $10,000 a month the day after closing

Portside's one sale this year was an original owner's, 29 years after the developer's closing, and the unit went straight to the rental market. One condominium transferred at 403 Main Street between January 1 and October 15, 2026, against two in the same window of 2025; $1,300,000 of volume against $1,950,000. The MLS record carries no floor area, so the site shows no per-foot figure; the listing record's 1,207 square feet put it at about $1,077, against $980 on last year's pair, $976 across four sales in 2024, $938 across three in 2023, $1,026 across four in 2022, $1,132 across the 12 sales of 2021, the most in any year, and $1,165 across seven in 2020.

#815N, a 1,207-square-foot top-floor corner two-bedroom with Bay and bridge views and new white oak floors, transferred at $1,300,000 on June 29; the listing record shows the original owners bought it from the developer on December 11, 1997 for $425,000, and that it was listed for rent at $10,000 a month from July 1 to September 9; its dues run $690 a month, which the listing credits to good reserves (Redfin). The building's #801N is listed at $1,190,000 with dues of $1,051, and #506N, a 910-square-foot one-bedroom with a den, closed at $910,000 with dues of $972 (Neighborhoods.com; MLSListings). A 2019 pairing ran the other way: #412N, bought at $1,225,000 in August 2016, sold at $1,200,000 (SocketSite, Aug 2019).

The building dates from 1997, eight residential floors on the east side of Main between Harrison and Bryant with a 24-hour attended lobby, a heated lap pool and hot tub over the Bay, gyms and a car-wash area, with parking at $210 a month; the street index shows more than 85 unit addresses, and the building record on this site lists 59 (Coldwell Banker, #801N; Redfin street index).

2026 so far, against the same window in 2025

Closings at The Portside between January 1 and October 15, 2026, set against January 1 to October 15, 2025. Days on market is median days from listing to contract on MLS-listed sales; "under 15 days" counts how many of those went into contract inside two weeks.

Year by year

Every recorded closing at The Portside since February 2020, by calendar year. 2026 runs through October 15, 2026. Days on market is available for MLS-listed sales from 2020 onward.

The building's highest median price per square foot in any year with five or more closings was $1,165 in 2020 (7 closings). The 2026 sale carries no floor area on the MLS, so there is no 2026 figure.

By bedroom count, 2025 against 2026

Every closing in 2026

All 1 closings through October 15, 2026, highest price first. Square footage and days on market are as recorded on the MLS; county-recorded transfers that never listed show no days.

Main Street, between Harrison and Bryant

Two blocks west at 325 Fremont, between Folsom and Harrison, a vacant 0.15-acre site with a prior approval for a 25-story tower of more than 100 homes was listed for sale at $15 million in July 2025 (SF YIMBY). Two blocks south on the waterfront, the Port executed new agreements with Strada on Piers 30-32 on October 24, 2025 and paused negotiations for 18 months over a $125 million infrastructure gap, with Seawall Lot 330 still planned for more than 600 homes (Port of San Francisco).

The nearest AI office is Anthropic's, three blocks north: all of 300 Howard and 342 Howard leased on February 2, 2026, with 400, 405, 500 and 505 Howard at First and Howard (BusinessWire).

The timetable that every South of Market building now sits inside is the public-offering calendar. Anthropic filed a confidential draft registration with the SEC on June 1, 2026, a week after a funding round that set its valuation at $965 billion (TechCrunch). As of this week the Standard reports the Anthropic listing has been pushed to November, after the midterms, that OpenAI's has moved to 2027, and that Anthropic is weighing a lockup longer than the usual six months (SF Standard). The same piece carries a Redfin estimate that current and former OpenAI and Anthropic employees could in theory buy close to a third of the metro area's homes with their proceeds, and the counter-argument from UC Berkeley's Enrico Moretti and the Bay Area Council's Jeff Bellisario that the money is concentrated in fewer hands than past booms and that these firms create fewer jobs per dollar because so much goes to data centers rather than headcount. The record in this report ends on October 15. None of it reflects a single share that has been sold.

Two citywide facts frame every building figure here. First, the office recovery is lopsided: CBRE put Q3 2026 vacancy at 27.7 percent citywide, down 6.6 points in a year, but Avison Young splits that into roughly 12 percent for Class A and north of 31 percent for Class B, and a Presidio Bay executive told Bisnow the headline number is misleading for that reason (Bisnow). Second, the condo market is still digging out: the Chronicle's May analysis found that only eight Bay Area ZIP codes showed inflation-adjusted condo gains over the year, all of them in San Francisco, and that Noe Valley's typical condo remained close to $400,000 below its 2019 level in real terms (SF Chronicle).

How this was counted

Two records feed this review. The MLS layer is one row per listing and carries days on market and square footage. The county layer reaches back further and catches transfers that never listed, but records the same closing once per data source, so the two were merged on unit, date and price and each closing kept once. Below-market-rate units and transfers under $300,000 are listed but excluded from every median. "Same window" means January 1 to October 15 of each year. Nothing here is a valuation of any unit, and nothing here is advice.

Tim McMullen · CA DRE #02016832
[email protected] · (415) 691-9272