The first American subway trip left New York City Hall heading north for Harlem 108 years ago today. The Independent Rapid Transit line connected Manhattans most traveled crossroads in one zig-zaging route. The first IRT line ran under Park Avenue South to Grand Central Terminal, crossed 42nd Street to Times Square, then up Broadway to 145th Street in Harlem -- a combination of today's 4/5, shuttle, and 1/2 lines.
A year later the route extended into the Bronx, then within five years, over to Brooklyn. Transit expansion was fast a century ago.
The subway quickly gained popularity because it was much faster than trolley cars and existing elevated trains. About 20 years later, New York got it's second subway company, the Brooklyn-Manhattan Transit company combining existing elevated lines in south Brooklyn with newer routes connecting to Manhattan. In 1932, Independent Subway launched, which, despite the name, was municipally-owned and operated.
In 1940 with the IRT and BMT both in deep financial trouble, the city absorbed the original subway lines and merged them with the IND, forming what is today's subway system, which hasn't expanded much since.