The Gowanus Canal begins at Butler Street in the neighborhood of Boerum Hill, in the northwestern part of Brooklyn. The wastewater pumping station at 201-234 Butler Street, a terracotta structure dating to 1911, is located north of the canal's head. The canal then runs in a south-southwest alignment parallel to the local street grid. Its course is located mid-block between Bond Street to the west and Nevins Street to the east. Along the way it passes bridges at Union Street, Carroll Street, and Third Street from south to north. While the Union Street and Third Street Bridges are movable bascule bridges, the Carroll Street Bridge is a retractable bridge that can be rolled diagonally to let ships through.