Brush Tunnel was built in 1911 of reinforced concrete and designed for two tracks on the Connellsville Extension of the Western Maryland Railway in Cash Valley, four miles west of Cumberland. The extension from Cumberland to Connellsville, Pennsylvania, was completed in 1912 at enormous cost through rugged and mountainous country. The line served a twofold purpose: providing a western outlet for the Western Maryland and an eastern tidewater outlet for the Pittsburgh and Lake Erie Railroad. It gave the Western Maryland the shortest line between Baltimore and Pittsburgh and the lowest grade line across the Allegheny Mountains. In 1915, a Baltimore to Chicago passenger train entered the tunnel before emerging into the Jennings Run Valley.