Who made locomotives?

Major US manufacturers in the steam era were the Baldwin Locomotive Works of Philadelphia, Pa, and the American Locomotive Company or (ALCO) in Schenectady, NY which were both regular producers for the PRR ( Baldwin) and the New York Central (Alco) as well as many other roads. some railroads evolved their own designs through the captive motive power departments such as the PRR"s Altoona Works- this would probably not be permitted today thanks (?) to diversification laws- not too different from antitrust statutes. a shipyard would not be permitted to run a steamship line, this type of consolidation would be taboo. Other US locomotive makers were General Electric (often in cooperation with Alco) and Lima Locomotive works, which merged with Baldwin in the fifties and manufactured CRANES well into the sixties and seventies. There are of course, the custom-builds by captive shops, as mentioned.