in Chicago, with over 75 in and around the metropolitan region during the early 1900s. Other cities where multiple railroads terminated or were major division points also had over 20 roundhouses, such as Boston, Cleveland, St. Louis, Sioux City, Indianapolis, and Cincinnati. The largest "as-built" roundhouse ever constructed is believed to have been the Boston and Maine's East Sommerville roundhouse outside of Boston (today the site of the Boston Engine Terminal). It was built with stalls long, of open space between the roundhouse and the turntable, and a turntable, giving it a diameter of . However, several roundhouses were enlarged over time that eventually became larger than the one in Boston. For example, the Union Pacific roundhouse in Cheyenne, Wyoming was lengthened in 1930 to accommodate the new 4-8-8-4 "Big Boy" articulated locomotives being delivered. After the expansion it was in diameter and constituted a near full-circle. A portion of this roundhouse still stands and is used by Union Pacific to store heritage rolling stock. The vast majority of roundhouses were torn down beginning in the 1950s as railroads converted motive power from steam to electric-diesel, which needed far less maintenance. Some were converted to service diesel engines, while others were used as storage or sold to other parties. Several dozen roundhouses stand today in active use by modern railroads and museums, although the majority of those still standing have been abandoned. An average of two per year are demolished or otherwise destroyed. The only roundhouse still in use as a locomotive servicing facility by the same railroad that constructed it is the Long Island engine house in Queens, New York. The largest surviving roundhouse by interior square footage is owned and operated by the North Carolina Transportation Museum in Spencer, North Carolina. It was built by the Southern Railway in 1924 and contains 37 stalls. The B&O Railroad Museum complex in Baltimore, Maryland contains the restored railcar maintenance roundhouse of the Baltimore and Ohio Railroad. Built in 1884, it is said to be the world's largest 22-sided building. The roundhouse in Aurora, Illinois, constructed in 1856, was purchased and restored by NFL football player Walter Payton. After Payton's death, the roundhouse was occupied by a micro-brewery and renamed Two Brothers Roundhouse, with a plaque mounted in Payton's honor. It is believed that this roundhouse is the oldest of its kind still standing in the United States. Operational roundhouses North