The <a href="https://en.wikipedia.org/wiki/Baltimore_and_Ohio_Railroad" id="mweA" rel="mw:WikiLink" title="Baltimore and Ohio Railroad">Baltimore and Ohio Railroad</a>'s new <i id="mweQ"><a href="https://en.wikipedia.org/wiki/Tom_Thumb_(locomotive)" id="mweg" rel="mw:WikiLink" title="Tom Thumb (locomotive)">Tom Thumb</a></i> <a href="https://en.wikipedia.org/wiki/Steam_locomotive" id="mwew" rel="mw:WikiLink" title="Steam locomotive">steam locomotive</a> races a horse-drawn car, presaging steam's role in U.S. railroads.