The Union named assistant Jim Curtin as interim coach Tuesday. Hackworth was 23-30-20 in two seasons, and led the Union to a franchise-best 12 wins in 2013.
The Union are 3-7-6 this season and are eighth in a 10-team MLS Eastern Conference.
Curtin played more than 200 games for the Chicago Fire and was chosen an MLS All-Star and the Fires defender of the year in 2004. He helped the squad to two U.S. Open Cup titles in 2003 and 2006, as well as the 2003 MLS Supporters Shield.
Curtin played his final two seasons in the League with Chivas USA before retiring in 2009.
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