The Baltimore and Ohio Railroad, the first common carrier railroad and the oldest railroad in the United States, was allocated the most number of USRA Light Mikado among over 50 railroads .
The Baltimore and Ohio Railroad (reporting marks B&O, BO) was the first common carrier railroad and the oldest railroad in the United States, with its first section opening in 1830. Baltimore and Ohio Railroad 100 With later copies, over 50 railroads used the type, including the following: 
