Original: The Interborough Rapid Transit Company (IRT) was the private operator of the original underground New York City Subway line that opened in 1904, as well as earlier elevated railways and additional rapid transit lines in New York City.
Simplified: The Interborough Rapid Transit Company (IRT) was the first operator of the original underground New York City Subway line that opened in 1904, as well as other earlier railways and rapid transit lines in New York City.