The area around Pittsburgh was originally inhabited by many groups of Native Americans. In the mid 1700s, the region was purchased from the Iroquois. The Lewis and Clark Expedition started in Pittsburgh at the beginning of the 1800s. During the Civil War, many Underground Railroad stations could be found in Pittsburgh. In the early 1900s, a substantial percentage of the national steel came from the Pittsburgh area. Today Pittsburgh has more than 400 bridges, even more than Venice, Italy, and so it is known as the “City of Bridges.” Many of the world’s first green buildings can be found in Pittsburgh. 800 sets of outdoor public stairways known as the Steps of Pittsburgh, attract many hikers and fitness walkers to the city. Other trails for biking and walking have been made near the rivers in the city of Pittsburgh. Pittsburgh is high on the list of most livable cities in the nation and the world.
One of the earliest industries in Pittsburgh was boat building. Pittsburgh has manufactured many materials, besides steel, including glass and aluminum. The railroads, the automotive industry and electronics have helped Pittsburgh's economy to grow in the past. Today, medical providers and technology firms are the leaders in the Pittsburgh economy. Leaders in these industries, that can be found in the Pittsburgh area, are Carnegie Mellon University, Allegheny Technologies, and the University of Pittsburgh Medical Center, the largest employer in the city. Modern office spaces for these companies can sometimes be found in renovated former factories. The area of Pittsburgh is headquarters for federal agencies in cyber defense, the nuclear navy and robotics. Pittsburgh is considered one of the top metropolitan areas favorable for business expansion.