Sioux Falls, S.D. ? Thousands of spectators gathered Saturday to watch the demolition of the city’s tallest building – but the Zip Feed Mill tower was no pushover.

The 202-foot-tall concrete structure dropped slightly, leaned a little – and stopped. Onlookers at viewing spots all over downtown groaned and gasped – with a few jokes mixed in.

“The leaning tower of Zip,” one woman said.

“The building won!” yelled another man, to the cheers of onlookers.

The abandoned feed mill elevator, widely considered the tallest building in South Dakota, was being demolished to make way for office and retail space.

The property owners had turned the event into a fundraiser for the Dakota chapter of the National Multiple Sclerosis Society. Residents bought T-shirts and $1 raffle tickets for the chance to trigger the blast, and stood outside with temperatures in the teens to view the tower’s demise.

Crews had drilled holes into the tower’s supporting columns and stuffed them with explosives, intending to drop the tower like a falling tree.

The bottom portion of the Zip Feed Mill tower in Sioux Falls, S.D., collapses Saturday during an attempted demolition of the building. After collapsing about 40 to 50 feet, the building remained standing, leaning to the east. The event was used as a fundraiser for the Dakota chapter of the National Multiple Sclerosis Society.

However, the rear of the tower was so rotten that it wasn’t stiff enough to push over, said Jim Redyke, president of blasting specialist Dykon Explosive Demolition of Tulsa, Okla.

“As the weight was transferred to the back side, it crushed the back walls and it crushed the basement wall,” Redyke said.

The tower collapsed into the structure’s basement and got wedged.

Crews planned to return to knock it down with a crane, but that might not occur until Thursday, said Jeff Hanson, spokesman for the site’s co-owners, Raven Industries Inc. and Howalt-McDowell Insurance Inc. Officials and the contractor in charge examined the site and determined the tower would hold, but the site remains fenced off and watched by security guards.

The blast may well have been enough to knock off the tower’s tallest building status. Qwest Tower in downtown Sioux Falls hadn’t been far behind at 195 feet.

The tower was opened in 1956, one of the most modern feed elevators of its time, but ceased operations in 2000. It sits on a bare lot in an industrial section just east of downtown along the Big Sioux River in this city of 134,000.

For much of its history, Sioux Falls’ largest employer was a livestock meatpacking plant. But about 25 years ago, Citibank moved its credit card division to Sioux Falls and started a change toward more white-collar jobs.

The Zip tower is being replaced by a $15 million office and retail center, and possibly a new events center.

Construction could begin this spring.

The raffle tickets raised $25,000 for the charity. Corporate sponsorships, VIP admissions and T-shirt sales were expected to raise the total past $140,000.