An employee in the team's engineering department, Cowell noticed his leather boots had dried up and shrunk over the summer. He wondered whether cowhide baseballs were doing the same thing in Denver's thin, bone-dry air.
Cavernous Coors Field was a place where home runs were launched like every day was an All-Star Home Run Derby, where pitchers feigned injuries or complained that it felt like they were throwing billiard balls.
Tests, some simple - such as dropping baseballs on concrete and noticing the dry ones bounced higher - and some scientific, proved Cowell's theory correct and the humidor was introduced in 2002.
Baseball at a mile high hasn't been the same since.
It will make its World Series debut tonight in Game 3 when Josh Fogg and the Rockies try to bounce back against Boston's Daisuke Matsuzaka after the Red Sox won the first two games at Fenway Park.
"What we found was the balls were getting smaller and traveling farther," Colorado manager Clint Hurdle said. "For a long time, it was unbeknownst to us. We would go, 'Oooh! and 'Ahh!' and watch them go. And everybody that came to the plate was homer ready."
The Rawlings balls had fallen below Major League Baseball's regulations, which require them to be between 5 and 5 ounces with a circumference of 9 to 9 inches. The Rockies sold MLB on the idea of a climate-controlled vault to store the baseballs in their boxes on metal racks.
The steel-walled room behind the Rockies clubhouse is always 70 degrees with 50 percent humidity. Baseballs are stored on large metal racks and rotated with each shipment, about four times a year.
Before games, 10 to 12 dozens of baseballs are rubbed with mud and returned to the humidor until game time.
It holds about 400 dozen baseballs and a new shipment of 142 came in this month for the World Series.
"Then, we'd be pitching with Titleists out there. Now we're pitching with Rawlings," Rockies pitching coach Bob Apodaca said. "Well-pitched games happen here consistently now."
Coors Field can play just like any pitcher's park, as evidenced by the Rockies' 2-1 squeaker over Philadelphia that wrapped up their sweep of the Phillies in the humidor's playoff debut this month.
There were 13.4 runs per game scored at Coors in the year before the humidor's introduction; that number was down by nearly three runs this season.
In 2001, there were a major league-high 268 homers hit out of Coors Field. This year, there were 185, which ranked 10th.
The Red Sox admit the humidor and its effects are a mystery to them.
"Cigars, right?" Boston second baseman Dustin Pedroia said. "I really don't know much about it. I'm not familiar with it."
"I just know that it works," Red Sox outfielder J.D. Drew said.
John Bohn, a physics professor at the University of Colorado, said the humidor has a greater effect on pitchers than hitters.
"It's not that the ball doesn't travel as far. It's that the pitchers have a better grip," he said.