Per league and club policy, terms of the two deals were not disclosed.
Harrington, who will turn 30 on Jan. 24, was part of Major League Soccer’s first free-agent class, and comes to Chicago to take the next step in a nine-year MLS career that has included stops in Kansas City, Portland and most recently Colorado.
"With his soccer intelligence and team-first attitude, Michael can start for us in a few different spots," said Fire general manager Nelson Rodriguez in a statement provided by the team. "He is solid on both sides of the ball and is an important addition for us."
Harrington’s natural position is left back, where the Fire have seen plenty of movement in the last week. On the first day of the 2016 MLS SuperDraft, they traded away Joevin Jones and selected Stanford standout Brandon Vincent with the fourth overall pick of the draft.
Over the course of his career, Harrington has played 221 regular-season MLS games (196 starts), amassing five goals and 18 assists. He has also appeared in nine MLS Cup Playoffs games (all starts) with Kansas City and Portland. Arguably his best season came in 2013, when he started all 33 games he appeared in for the Timbers plus all four playoff games in their run to the Western Conference Championship game for a total of 3,311 minutes played that year. In 2015, his only season in Colorado Harrington appeared in 14 games for the Rapids and none after July 18.
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McLain, 27, returns to MLS after spending two years in USL, first with the Orange County Blues in 2014 and then with Sacramento Republic FC in 2015. McLain’s first stint in MLS came with Chivas USA, who signed him ahead of the 2012 season. He made his MLS debut in 2013, one of two games he has played in the league.
In his most recent season with Sacramento, McLain made 29 appearances for the Republic, allowing 30 goals while recording 71 saves, six shutouts and a 1.25 goals against average en route to a 11-8-5 record. His option was declined by Sacramento at the end of the year.
"Perhaps not yet recognized by many, we believe that Patrick is about to become known as an outstanding talent," said Rodriguez. "He's excellent with his feet and he also commands his box very well."
The Fire have now filled 17 of the 28 roster spots available to them, meaning more signings will almost certainly follow as the team continues to re-shape itself under the first-year GM/coach duo of Rodriguez and Veljko Paunovic.