This 1913 photo of Lexington Avenue, between 105th and 106th Streets in Manhattan shows a construction method called cut and cover. Like the name suggests, this method involved cutting or digging a trench in the street, installing the necessary infrastructure, and then covering with the street on top. During construction business went on as usual around construction. With temporary wooden structures placed over the work below, trolleys and other traffic were able to pass over top of the construction. Many of our first subway tunnels were built using this method beginning in 1900, which made construction faster, cheaper, and easier than trying to dig deep under the ground. It allowed sand hogs (the nickname given to tunnel workers) to avoid the difficult and unstable bedrock underneath most of Manhattan called Manhattan schist.