ST. LOUIS • Even a half-hour before the sale started, the seats in a fourth-floor courtroom downtown were quickly filling up.

By 9 a.m. Tuesday in the Civil Courts building, it was standing room only, with onlookers pressed shoulder to shoulder along the walls, enduring occasional chiding from a sheriff’s deputy to remove their caps, silence their cellphones and keep quiet.

Tuesday was tax sale day, so the room bustled with excitement at the prospect of picking up St. Louis properties on the cheap from owners who hadn’t paid their property taxes for years. There were a few suits and ties, but the prospective investors came in track suits, shorts, a Superman T-shirt and a crop top.

Outside, in the fourth-floor lobby, a gaggle of potential bidders formed around a bulletin board with a legal notice showing whether the properties they had been eyeing were still for sale.

Up until the sheriff’s sale started at 9 a.m., owners whose property was at risk of being auctioned for back taxes could still hustle to City Hall and pay what they owed. Bidders could not be sure until they entered the courthouse that the property they most wanted would be auctioned.