who is the founder of this team?
Bob Howsam.
Denver Broncos
The Denver Broncos were founded on August 14, 1959, when Minor League Baseball owner Bob Howsam was awarded an American Football League (AFL) charter franchise. 
what is thunder (mascot)? A horse that is also an official live animal mascot. what is its duties as the last? The duties include leading the team onto the field at the start of every home game, and a gallop down the length of the field whenever the team scores a touchdown or field goal. which team are you talking about? The Denver Broncos Football Team. does it appear for any other match or team? It appears only for every match of the said team .
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Denver Broncos [SEP] 1960–1969: AFL era
The Denver Broncos were founded on August 14, 1959, when Minor League Baseball owner Bob Howsam was awarded an American Football League (AFL) charter franchise. The Broncos won the first-ever AFL game over the Boston Patriots 13–10, on September 9, 1960. On August 5, 1967, they became the first-ever AFL team to defeat an NFL team, with a 13–7 win over the Detroit Lions in a preseason game. However, the Broncos were not successful in the 1960s, compiling a record of 39–97–4 during their ten-season run in the AFL. Denver came close to losing its franchise in 1965, until a local ownership group took control and rebuilt the team.