In the standard Monopoly board game, the railroad between Pennsylvania Railroad and Short Line is B. & O. Railroad.
The four classic railroad spaces are Reading Railroad, Pennsylvania Railroad, B. & O. Railroad, and Short Line. Their names reflect American railroad companies or railroad traditions used in the game’s classic property design.
B. & O. stands for Baltimore and Ohio, one of the historic railroads associated with the United States. On the board, it occupies the railroad position between Pennsylvania Railroad and Short Line when the properties are read in sequence.
Players sometimes remember the four railroads by their locations rather than their names, and editions outside the United States may localize names or graphics. The answer applies to the standard classic American board.