Democratic Rep. Conor Lamb is facing Sean Parnell in Pennsylvania's 17th Congressional District.
The western Pennsylvania district encompasses the Pittsburgh suburbs and is home to all of Beaver County.
According to Business Insider, Lamb currently serves as the Vice-Chair of the House Committees on Veterans Affairs.
Lamb is also on the House Committee on Science, Space, and Technology and the Committee on Transportation and Infrastructure.
Parnell is a decorated military veteran and Army Ranger who has been awarded two Bronze Stars and a Purple Heart.
Polls began closing in the district at 8 p.m. EST.