PRR 3750 is a Pennsylvania Railroad K4s steam locomotive located in the Railroad Museum of Pennsylvania, outside of Strasburg, Pennsylvania in the United States. For over a decade, 3750 stood in for the prototype K4s, 1737, and was listed on the National Register of Historic Places in 1979. It is one of the two remaining K4s locomotives and, along with PRR 1361, was designated the official state steam locomotive in 1987 by the Pennsylvania General Assembly.