The Indianapolis Colts have competed in the NFL since 1953, when they began in Baltimore. The Colts were one of the three original NFL teams to join the American Football League (AFL) to form the AFC after the 1970 merger.

When they were known as the Baltimore Colts, they were a playoff team 10 times and they won three NFL Championships -- in 1958, 1959 and 1968. The Colts also played in two Super Bowls. They lost to the New York Jets in Super Bowl III and defeated the Dallas Cowboys in Super Bowl V.

In 1984, the Colts relocated to Indianapolis. Since then, they've made the playoffs 16 times, won two AFC championships, and defeated the Chicago Bears in Super Bowl XLI.

The Colts have had some great players since becoming an NFL franchise. But when it comes down to the best of the best, which players can line up on the Mount Rushmore of Colts? Read below for a list of the four greatest players in franchise history.

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PEYTON MANNING

Peyton Manning, the greatest quarterback in franchise history, is also recognized as one of the best players of all-time. (Photo by Rob Tringali/Sportschrome/Getty Images)

Peyton Manning is not only the greatest quarterback in Colts history, but he is arguably a top-five player at the position in NFL history as well. Manning, the No. 1 pick in the 1998 NFL Draft, was under center for the Indianapolis Colts for 14 seasons. He led the franchise to eight AFC South titles, two AFC Championships and one Super Bowl victory.

Manning, a record five-time NFL MVP, was a 14-time Pro Bowler, seven-time first-team All-Pro and three-time second-team All-Pro selection. He led the league in passing yards three times and passing touchdowns four times, was named the NFL Comeback Player of the Year in 2012, and honored as the Walter Payton NFL Man of the Year in 2005. He currently holds NFL records for the most passing touchdowns in a single season (55), the most passing yards in a season (5,477), and is tied for the most passing touchdowns in a single game (7).

Manning, who was already inducted into the Colts' Ring of Honor, was a part of the NFL's 2000s All-Decade Team and the NFL's 100th Anniversary All-Time Team. He will undoubtedly become a first-ballot Hall of Famer in 2021.

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JOHNNY UNITAS

Johnny Unitas, who spent his career with the Baltimore Colts, won Super Bowl V against the Dallas Cowboys. (Photo by © Wally McNamee/CORBIS/Corbis via Getty Images)

Johnny Unitas, nicknamed "The Golden Arm", is another quarterback considered to be one of the greatest of all-time. Unitas, a Super Bowl V champion, won three NFL Championships with the Baltimore Colts -- in 1958, 1959 and 1968. He's a three-time NFL MVP, a 10-time Pro Bowler, five-time first-team All-Pro and three-time second-team All-Pro.

Unitas held the record for most consecutive games with a touchdown pass -- set between 1956 and 1960 -- until it was broken by New Orleans Saints quarterback Drew Brees in 2012. Unitas led the league in passing yards and passing touchdowns four times, and he was a part of the NFL's 1960's All-Decade Team, as well as the NFL's 50th, 75th, and 100th Anniversary All-Time Teams.

Unitas' No. 19 jersey is retired by the Colts.

MARVIN HARRISON

Hall of Famer Marvin Harrison is one of the best wide receivers in league history. (Photo by Al Messerschmidt/Getty Images)

Marvin Harrison, who was drafted by the Colts in the first round of the 1996 NFL Draft, is one of the greatest wide receivers in NFL history. A Super Bowl XLI champion with the Indianapolis Colts, Harrison was an eight-time Pro Bowler, three-time first-team All-Pro, and five-time second-team All-Pro.

Harrison led the NFL in receiving yards (1999, 2002), and receptions twice (2000, 2002), and he was the co-leader in receiving touchdowns in 2005. Harrison held the record for most receptions in a single season (143) for over 10 years, but it was broken by New Orleans Saints wide receiver Michael Thomas in 2019.

Harrison, a member of the Colts' Ring of Honor, was a part of the NFL's 2000's All-Decade Team, as well as the NFL's 100th Anniversary All-Time Team.

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GINO MARCHETTI

Gino Marchetti, of the Baltimore Colts, is one of the best defensive ends in league history. (Photo by Diamond Images/Getty Images)

Gino Marchetti, an all-time great defensive end, played for the Baltimore Colts from 1953 to 1966. He was a two-time NFL champion (1958 and 1959), an 11-time Pro Bowler and 10-time All-Pro selection, which includes nine first-team honors. Marchetti was inducted into the Pro Football Hall of Fame in 1972.

Marchetti, a member of the NFL's 1950's All-Decade Team, was also recognized on the NFL's 50th, 75th, and 100th Anniversary All-Time Teams as well.