The B&O, Pennsylvania, and Santa Fe, each made a point of saving various locomotives from the steam era, as permanent collections, each intending to see them historically interpreted. U.P. kept one operational and later added another, while housing two donor locomotives.
Did any other railroad companies maintain a collection of varied motive power on their own property, for similar historical purposes? I think such policy showed remarkable foresight, in an era when many railroads couldn't wait to clean their property of the physical presence of steam.

The C&O kept a few locomotives and rolling stock for their own historical collection. They were the 611(614), 2705, 1604, 1309, 460 and 377. The 377 was frequently displayed at fairs and such along with either the combine, 409, or a wooden caboose, 90382.

Canadian National Railways had a travelling museum train during the latter steam era and maintained a historical collection of steam locos and rolling stock. Much of this was disbursed in 1967. They also operated steam excursions from the end of regular steam in 1960 every year (except 1972) until 1980 when the last ecursion engine, 4-8-2, 6060 was sold to the Govt. of Alberta.

Canadian Pacific Railway also set aside many steam locos for preservation and later maintained a diesel and rolling stock collection.

As far as streetcars go, several companies had historical collections. Toronto, Montreal, Baltimore, Chicago and others had substantial collections, most of which were eventually preserved in volunteer-based, operating museums.

Gord

Some of the electric railway companies had "Historic Collections" including Baltimore and I believe Washington DC... The Baltimore collection is the basis to the electric railway museum in that city, and is a wonderful study in very old electric railway equipment...

Yes, the Baltimore Streetcar Museum's collection is the result of the "attic horde" of the old United Railways/Baltimore Transit Co., shunted about from carhouse to carhouse (sometimes in secret) until they were donated to the Md. Historical Society in 1954. They eventually became part of what would later become the National Capital Trolley Museum, then in a city-owned park just north of Baltimore proper, but a split developed, with the BSM being formed in 1966 and the Baltimore cars being appropriated for the BSM project.

Until recently, the BSM was one of the few such museums, if not the only one, with equipment from only one city. That changed when the Friends of the Phila. Trolley brought down a Philly PCC and the BSM went for a Philly snowsweeper and a St. Louis-built PCC (El Paso/San Diego) to rebuild for handicapped access.