The Three Sisters of Pittsburgh

Located in the rugged terrain of deep valleys and rivers, Pittsburgh has been affectionately known by many as the “City of Bridges”. These bridges were necessary for the early settlers to overcome the tough challenges, they helped them connect newly constructed highways and enabled Pittsburgh to grow into an industrial powerhouse.

*Aerial Photo of the Three Sister Bridges*

One of the famous sets of bridges in Pittsburgh is the Three Sister Bridges, which sits on Sixth, Seventh, and Ninth Street. Prominent in Aztec Gold, which is a nod towards Pittsburgh’s Black and Gold colors, these bridges are a rare example of identical trio bridges built in the U.S.

In 1899, Congress passed the River and Harbor Act which resulted in the Secretary of War declaring bridges over navigable bodies of water in violation if they posed an obstruction to navigation due to insufficient height or width. The bridges in Pittsburgh officially became obstructions in 1917, resulting in the birth of the “Three Sisters” bridges. Designed by Allegheny County engineers, the bridges were built by the American Bridge Company between 1926 to 1928.

*The Deutz Suspension Bridge in Cologne, Germany that the Three Sisters were designed after.*

The Art Commission, which was the advisory body, created by the state in 1911 to approve bridges in Pittsburgh vetoed initial proposals. It sought for new bridges that would not mar the downtown skyline with metal structures above the deck. Suspension bridges instead of truss bridges were favored, as this would allow people to travel on the bridge and look at Pittsburgh without any supports obstructing their view. Architects were hired and eventually, developed a similar design to the Deutz Suspension Bridge in Cologne, Germany. This architectural design was meant to be a piece of art in and of itself and resulted in making the “Three Sisters” its own tourist attraction.

The Sister Bridges are Self-Anchoring Suspension Bridges. Instead of being anchored to the land, the weight of the bridge itself acted as the anchor. During construction, the bridges were built from both sides of the river. A cantilever technique was used to mesh the two sides together. This cantilever allowed the deck to be fixed at one end, and built further out to meet the other end of the deck. The 7th and 9th Street Bridge finished construction in 1926. The 6th Street Bridge was finished in 1928, and was named the “Most Beautiful Steel Bridge of 1928” by the American Institute of Steel Construction.

Today, our three sister bridges might be more recognized by their names.

The 6th Street Bridge was named after Roberto Clemente in 1998, in honor of the Pirates Hall of Fame player.
The 7th Street Bridge was named after Andy Warhol in 2005, after the famous Pittsburgh-born American visual artist and film director.
The 9th Street Bridge was named after the author and environmentalist Rachel Carson.