Shortly after kickoff Saturday, the fans who will gather on Cal’s Tightwad Hill should raise a cup to the sad memory of the original Big Game freeloaders back in 1900.

Warning: This is a ghastly story. I stumbled across it while searching for some interesting Big Game history. Even after 116 years, the accounts of this Thanksgiving Day tragedy are hard to read.

That 10th Big Game was played at old Recreation Park, at the corner of 16th and Folsom in what is now the Mission District but was then a grimy industrial area. On a glorious, sunny day, the game drew 19,000 fans, the largest sports crowd ever West of the Mississippi.

Many of the folks who were either shut out or priced out ($1 tickets) found a perch to watch the game for free. Just across the street from the stadium was the brand-new San Francisco and Pacific Glass Works building, and 400 to 500 boys and men climbed onto the building’s metal roof, nearly five stories high, for a splendid view of the game.

About 20 minutes after kickoff, the roof collapsed — “Sprung open like a gallows trap,” one survivor said — raining about half the boys and men down onto the blazing-hot, brick cover of a vat filled with 15 tons of burbling molten glass.

“Plunge to Their Death on a White Hot Furnace,” The Chronicle’s front-page headline read.

The Evening News in San Jose went with “Sizzling, Shrieking Human Mass.”

In the end, 22 would die and more than 100 others would suffer burns and assorted injures from their 45-foot fall. As rescuers fought desperately to save lives and stack corpses, the game went on.

Stanford won 5-0 on a last-minute field goal. (A field goal counted for five points until 1904.)

Some saw this tragedy coming. At the 1897 Big Game, also on a Thanksgiving Day at Recreation Park, hundreds of boys climbed onto the grandstand eaves. One section collapsed and a boy was slightly injured. The man in charge of grandstand construction went on high alert. Surveying the neighborhood before the 1900 game, the man identified the Glass Works roof as a danger spot, and ordered Works supervisor James Davis to take security measures. Davis was given six game tickets as incentive for keeping his roof clear.

Alas, as game time neared, the mob outside the stadium began to eye the Glass Works building’s roof. The factory was protected by an 8-foot wooden fence topped with barbed wire, but kids tunneled under the fence and broke open the gate. Hundreds rushed in, ignoring the shouts and threats of Davis, who was waving a metal pipe. The mob climbed fire escapes and ladders onto the roof, packing in like standing sardines.

As Davis and other employees ran to summon police, the kids on the roof were in good spirits. One of them, Charles Taylor, told The Chronicle, “Some of the fellows said, ‘If this thing breaks, we’ll all go down together.’”

About 20 minutes after the 2:30 kickoff, the thing broke. The metal collapsed inwardly, forming a funnel that dropped about 100 of the men and boys onto the rounded brick cover of the 30-by-62-foot furnace, which had been cranked up, the glass heated to 3,000 degrees.

The Chronicle’s account said the “outer firebricks of this seething inferno were so hot that a man’s boots would be consumed in the time it would take him to run across the surface.”

The story, which took up the entire front page and counted only 14 dead one day after the accident, described a grisly scene: “So sudden and complete was the wreck that few if any of those astride the roof had an opportunity to save themselves.

”The mass of human beings plunging to death or crippling hurt below presented a horribly sickening spectacle.”

From a competing news account: “Many of the victims caught at the rafters and girders as they fell and clung desperately, shrieking for assistance. One by one, however, they dropped into the fiery furnace (covers), which were literally covered with writhing bodies. ...

“The situation was rendered more horrible by the fact that the sudden derangement of the furnace machinery sent a stream of boiling oil over the bodies of the victims.”

Two workers used glass-stirring poles to pull men and boys, dead and alive, off the furnace cover, saving dozens of lives.

One rescuer said, “We stood beside a veritable hell, and saw men roasting to death before our very eyes.”

One boy, Thomas Curran, fell through the roof but wrapped his legs around a ceiling support. “As I clung there,” he said, “I saw the poor fellow who had been chatting with me strike the furnace. He curled up like a worm in the heat.”

Inside the stadium, the roof collapse boomed like thunder. The crowd was distracted for a moment, then a Cal fan shouted, “It’s a job!”— some kind of Stanford trick.

The game continued, even as ushers walked the aisles, calling for doctors.

Stanford, coached by Fielding Yost, went into this season-ending game with a 6-2 record, but one loss was to Stanford’s alumni team, on which Yost played fullback.

This Thanksgiving Day thriller was decided on a field goal by tackle William Traeger, a law student who would become a Republican U.S. Representative. It was the last Big Game played on Thanksgiving.

The scene in San Francisco after the game had to be as strange as any in the city’s history.

The city went into full medical emergency. Calls went out for doctors, and horse-drawn vehicles carried the wounded and dead to hospitals and morgues, outside of which thousands clamored, desperate for news of the victims.

After the game’s final gun, fans stormed the field and lifted Stanford’s gridiron heroes onto their shoulders, then paraded them down Market Street to the Palace Hotel, where the party raged.

So have fun Saturday up there on Tightwad Hill, folks, but spare a thought for the boys on the roof 116 years ago.

Scott Ostler is a San Francisco Chronicle columnist. Email: sostler@sfchronicle.com Twitter: @scottostler