The Trappers joined the PCL in 1981 when Edmonton businessman Peter Pocklington purchased the Ogden A's franchise from Utah trucker Dennis Job. The team's games were originally played in Renfrew Park (later John Ducey Park). The Trappers were immediately popular with the community, often above the league average in attendance attracting almost half a million fans every season. A total of 8 million fans came to see them play over the course of their 24 year existence.
In 1984, the Trappers (who, at the time, were the Triple-A farm team of the California Angels) became the first Canadian franchise to win a championship. They were also the first and only to win a PCL Championship and first to win a championship under affiliation. The manager was Moose Stubing.
In 1995, John Ducey Park was torn down and replaced by Telus Field where the Trappers celebrated three PCL titles in their last decade, most recently in 2002 under the affiliation of the Minnesota Twins. In 2003, the team became the major affiliate of the Montréal Expos. Edmonton was the most successful, longest running, and second last triple A team in Canada which gave the city of Edmonton the name Baseball City of Canada.
On June 11, 2004, future Toronto Blue Jays pitcher Scott Downs threw a no-hitter against Las Vegas. It was the first no hitter by a Trapper since August 8, 1996 when Aaron Small threw one against the Vancouver Canadians.
Edmonton qualified for playoffs for the last time in history in September 2003 when the defeated the Portland Beavers to make the post-season but were eliminated immediately by the Sacramento Rivercats 3 games to 0.
In October 2003, the Trappers' fate in Edmonton was sealed when the team was purchased by a group led by Baseball Hall of Famer Nolan Ryan and his son Reid. The sale shocked many fans in Edmonton. The Ryans moved the team after the 2004 season to Round Rock, Texas, where it is now known as the Round Rock Express. The last home game, a sizeable crowd filled the stadium to give the Trappers a final sendoff against the Las Vegas 51s. The game, however, was rained out after only one inning.