The train collection includes some of the biggest, oldest, and most singular rail heritage artifacts in existence, including the biggest successful steam engine, UP #4006, the "Big Boy"; the biggest diesel-electric engine, UP #6944, the "Centennial"; the biggest railroad tank car, GATX #96500, the "Whale Belly"; and the biggest railroad snowplow, UP #900081. It also includes the oldest rail heritage vehicle in the collection, a B&P horse-drawn rail coach; the oldest locomotive in the collection, the B&P "Daniel Nason"; and the oldest operational diesel-powered switcher, Arkansas & Missouri #22. Singular surviving artifacts include the only remaining Katy Railroad steam engine, MKT #311; the only surviving inspection locomotive, Reading "Black Diamond"; and the only known example of its kind in the U.S., the Sellers Turntable.