It is a branch of the IRT White Plains Road Line in the northeastern section of the Bronx, north of East 180th Street.

The NYW&B opened in 1912, providing service from the Harlem River to White Plains and New Rochelle (eventually to Port Chester).

The following services use part or all of the IRT Dyre Avenue Line:[2] It is served by the 5 train, which makes all stops.

A fourth track briefly joins south of Eastchester–Dyre Avenue and between Pelham Parkway and Morris Park.

The fourth track (a trackbed for most of its length) was extended to test subway automation on the line and was initially used for layup and storage.

The northbound express track was used for storage but this use has largely been made redundant by the expansion of Unionport Yard.

The other portion has been extended to the northern end of Pelham Parkway in conjunction to the signal modernization project on the line.

However, a track connection to the NHRR was built in 1955 for equipment and material transfer and interchanges, including new car deliveries.

[15] The New York City Board of Transportation (BOT) bought the NYW&B within the Bronx north of East 180th Street in April 1940 for $1,800,000 and rehabilitated the line.

The Board of Transportation rehabilitated twenty old surplus gate cars, numbered 1580–1587, 1589–1600, and 107, that were operating on the Third Avenue Elevated to use on the line.

[9][17] On March 19, 1941, a trailing point was built in from the existing White Plains Road Line to the former Track 3 of the NYW&B just north of the East 180th Street station, near the original IRT tower, and under the present Bronx River Parkway bridge.

This granted access to the newly BOT-owned line for construction purposes, specifically re-electrification and signaling.

[19] For a few years, the line retained the 11,000-volt catenary on the express tracks in case service to Westchester was resumed.

By this time some middle trackage had been restored as “Y3 and Y4” through Morris Park station and south of Dyre Avenue.

[32] On February 27, 1962, the Transit Authority announced a $700,000 modernization plan of the Dyre Avenue Line.

[3] In 1986, the New York City Transit Authority launched a study to determine whether to close 79 stations on 11 routes, including the entire Dyre Avenue Line, due to low ridership and high repair costs.

[42][43] Numerous figures, including New York City Council member Carol Greitzer, criticized the plans.

[43][44] The siding connection between the Dyre Avenue Line at East 180th Street and the Penn Central (former New Haven Railroad) was discontinued on August 12, 1975, and the third rail was removed south of the station in 1979, where retired IRT subway cars were stored, and as of 1979 the physical connection between the line and what is now the Amtrak Northeast Corridor/CSX was permanently removed.

[18] The elevated structure between East 177th and Lebanon Streets was dismantled in the early 2000s, and housing was built on part of the former rail line's right-of-way in 2013.