Grist Mill Walking Bridge

The Grist Mill Walking Bridge is the third bridge at this location. It is a cable-stayed footbridge that was built in 2006.

The original bridge was called the Patterson Viaduct. It was one of three viaducts built by the Baltimore and Ohio Railroad (B&O) in 1829 as part of the Old Main Line. The viaduct was constructed out of granite blocks and had four graduated arches. Two of these arches were 55 feet long and spanned the river. The other two arches were 20 feet long and allowed passage of county roadways on each side of the river. The arch that spanned the roadway on the west bank still remains and was incorporated into the future bridges. The east abutment and retaining wall are also still intact. The rest of the viaduct was destroyed by a flood in 1868.

The bridge was replaced in 1869 by a single span Bollman Truss. This bridge was abandoned when the Ilchester Tunnel was opened in 1903, and the rail track was moved to a new bridge upstream of the existing bridge. It is unclear when the truss bridge was actually demolished.

The Patapsco Valley State Park was created in 1907. In 2003, a project was started within the park to create a multi-use section of trail. The original trail terminated at the old railroad bridge abutment, but in 2006 the project was continued to connect to the local roadways. This included the construction of the suspension bridge. The abutment and arch span from the original bridge was reused, and the towers of the new bridge were designed to echo the architecture of the Bollman Truss Bridge.