In 1872, Baldwin was appointed the head architect for the Baltimore and Ohio Railroad, a position previously held by John Rudolph Niernsee, his mentor. Over the next 25 years he designed stations and other structures for the railroad, including many of its most famous buildings. Perhaps the best known are the passenger and freight car shops at Mount Clare Shops established in 1829 by the railroad at its beginnings in 1829 in southwest Baltimore that includes his 1884 central roundhouse at the current B&O Railroad Museum (established 1953), the B&O passenger station (1875) at Point of Rocks, Maryland and the immensely long B&O Warehouse (1905) adjacent to Camden Street Station (now at the Camden Yards sports stadiums complex in downtown Baltimore. Other surviving Baldwin stations can be found in: