23rd Street was a station on the demolished IRT Third Avenue Line

IRT Third Avenue Line

The IRT Third Avenue Line, commonly known as the Third Avenue El, was an elevated railway in Manhattan and the Bronx, New York City. Originally operated by an independent railway company, it was acquired by the Interborough Rapid Transit Company and eventually became part of the New York subway...

. It had two levels. The lower level was served by local trains and had two tracks and two side platform

Side platform

A Side platform is a platform positioned to the side of a pair of tracks at a railway station, a tram stop or a transitway. A pair of side platforms are often provided on a dual track line with a single side platform being sufficient for a single track line...

s. It was built first. The upper level was built as part of the Dual Contracts and had one track with two side platforms and served express trains. The next stop to the north was 28th Street

28th Street (IRT Third Avenue Line)

28th Street was a station on the demolished IRT Third Avenue Line. It had two levels. The lower level was served by local trains and had two tracks and two side platforms. It was built first. The upper level was built as part of the Dual Contracts and had one track that bypassed the station and...

 for local trains and 34th Street

34th Street (IRT Third Avenue Line)

34th Street was a station on the demolished IRT Third Avenue Line. The station was served by Third Avenue local trains and a shuttle to the 34th Street Ferry. Third Ave service originally had two tracks and two side platforms. During the Dual Contracts, a center express track was built...

 for express trains. The next stop to the south was 18th Street

18th Street (IRT Third Avenue Line)

18th Street was a station on the demolished IRT Third Avenue Line. It had two levels. The lower level was served by local trains and had two tracks and two side platforms. It was built first. The upper level was built as part of the Dual Contracts and had one track that bypassed the station and...

 for local trains and Ninth Street for express trains. The station closed on May 12, 1955.