Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Charles River Bridge is a pair of railroad single-leaf, through-truss, rolling bascule bridges across the Charles River that connects North Station in Boston, Massachusetts to MBTA Commuter Rail lines in northern Massachusetts. These bridges were designed by Keller & Harrington of Chicago, Illinois and built by the Phoenix Bridge Company of Phoenixville, Pennsylvania. Each bridge uses a 629-short-ton over-head concrete counterweight. Originally, there were four bridges, but only two of them remain.