The move signified a farewell to Kelvin Beachum, who was close to signing with the Jacksonville Jaguars.
Beachum was a seventh-round draft pick by the Steelers in 2012. He started five games at right tackle as a rookie before starting 34 regular-season games and one playoff game at left tackle from 2013-15.
Beachum suffered a torn ACL in the sixth game last season and was placed on IR. He was replaced at left tackle by first-year player Alejandro Villanueva, who started the final 10 games in the regular season and then both playoff games.
Harris provides the Steelers with competition for Villanueva, while both can also play right tackle for starter Marcus Gilbert if needed.
Harris is actually considered a better right tackle than left but started all 16 games at left tackle for the world champion Denver Broncos last season.
It was Harris' second stint with Denver after bouncing to three other teams since the Broncos drafted him in the third round out of Notre Dame in 2007.
A high school All-America out of St. Paul, Minnesota, Harris was a three-year starter at Notre Dame. He measured 6-4 1/2, 305 at the Combine in 2007 and was timed in the 40 at 5.09. He was considered by scouts to be a natural knee-bender whose lacked a bit of strength. He benched only 22 times at his Combine.
Harris became Denver's starting right tackle in 2008 and stayed there through the middle of 2009 before two dislocated toes forced him to injured reserve.
Harris returned to start 10 games at right tackle in 2010 and was signed the next offseason by Philadelphia. However, Harris underwent back surgery and was waived injured before sitting out the 2011 season.
Harris became a reserve swing tackle for Houston in 2012-13 and then signed with Kansas City in 2014 and started 15 games at right tackle.
The Broncos re-signed Harris in 2015 to replace the injured Ryan Clady at left tackle. Harris played the second-most number of snaps out of all Broncos linemen last season.
His 70 career starts and relative lack of penalties over the years led Pro Football Focus to call Harris "a disciplined, durable player."