Prospect Avenue station (BMT Fourth Avenue Line)

The Prospect Avenue station was constructed as part of the Fourth Avenue Line, the plan for which was initially adopted on June 1, 1905.[8] The Rapid Transit Commission was succeeded on July 1, 1907, by the New York State Public Service Commission (PSC), which approved the plan for the line in late 1907.[9][10] The contract for the section of the line that included the Prospect Avenue station, Route 11A3, which extended from 10th Street to 27th Street, was awarded on May 22, 1908, to the Tidewater Building Company and Thomas B. Bryson for $2,043,162.31 (equivalent to $66,547,000 in 2022). The New York City Board of Estimate approved the contract on October 29, 1909.[9][11] Construction on the segment started on December 20, 1909, and was completed in May 1912.[8]

As part of negotiations between New York City, the Brooklyn Rapid Transit Company (BRT), and the Interborough Rapid Transit Company for the expansion of the city's transit network, the line was leased to a subsidiary of the BRT. The agreement, known as Contract 4 of the Dual Contracts, was signed on March 19, 1913.[9] Prospect Avenue opened on June 22, 1915, as part of an extension of the subway to Coney Island, which included the Fourth Avenue Line north of 59th Street as well as the entire Sea Beach Line.[12][4] The station's opening was marked with a competition between two trains heading from Chambers Street station in Manhattan to the Coney Island station, one heading via the West End Line and the other via the Sea Beach Line; the latter got to Coney Island first.[4]

On June 27, 1922, the New York State Transit Commission commissioned its engineers to examine platform-lengthening plans for 23 stations on the lines of the Brooklyn–Manhattan Transit Corporation (BMT), the successor to the BRT, to accommodate eight-car trains. As part of the project, Prospect Avenue's platforms would have been lengthened from 435 feet (133 m) to 530 feet (160 m).[13][14] Though the Transit Commission ordered the BMT to lengthen these platforms in September 1923, no further progress was made until February 16, 1925, when the New York City Board of Transportation (NYCBOT) commissioned its engineers to examine platform-lengthening plans for this and eleven other stations along the Fourth Avenue Line. It estimated the project would cost $633,000 (equivalent to $10,563,000 in 2022).[15] The NYCBOT received bids for the project on February 25, 1926.[16] The contract was awarded to the Corson Construction Company for $345,021 (equivalent to $5,703,000 in 2022).[17] The extensions opened on August 1, 1927.[6]

The city government took over the BMT's operations on June 1, 1940.[18][19] In July 1959, the New York City Transit Authority (NYCTA) announced that it would install fluorescent lighting at the Prospect Avenue station and five other stations along the Fourth Avenue Line for between $175,000 and $200,000. Bids on the project were to be advertised on August 7, 1959 and completed by fall 1960.[20]

In the 1960s, the NYCTA started a project to lengthen station platforms on its lines in Southern Brooklyn to 615 feet (187 m) to accommodate 10-car trains.[7] On July 14, 1967, the NYCTA awarded a contract to conduct test borings at eleven stations on the Fourth Avenue Line, including Prospect Avenue, to the W. M. Walsh Corporation for $6,585 (equivalent to $57,793 in 2022) in preparation of the construction of platform extensions.[21] The NYCTA issued an invitation for bids on the project to extend the platforms at stations along the Fourth Avenue Line between Pacific Street and 36th Street, including those at Prospect Avenue, on March 28, 1969.[22] Funding for the renovation projects came out of the NYCTA's 1969–1970 Capital Budget, costing $8,177,890 (equivalent to $65,260,000 in 2022) in total.[23]

As part of the renovation project, the station's platforms were extended,[7] and the station's elaborate mosaic tile walls were covered over with 8-by-16-inch (20 by 41 cm) white cinderblock tiles. The latter change, which was also made to 15 other stations on the BMT Broadway and Fourth Avenue Lines, was criticized for being dehumanizing. The NYCTA spokesman stated that the old tiles were in poor condition and that the change was made to improve the appearance of stations and provide uniformity. Furthermore, it did not consider the old mosaics to have "any great artistic merit".[24]

Under the Metropolitan Transportation Authority's 2015–2019 Capital Program, the station, along with thirty other New York City Subway stations, were scheduled to undergo a complete overhaul as part of the Enhanced Station Initiative. Upgrades were to include cellular service, Wi-Fi, USB charging stations, interactive service advisories and maps.[25][26] From January to May 2016, Grimshaw Architects worked on a design for the station's renovation, with Arup Group acting as a consultant.[27] The contract for Package 1 of the renovations, which covers renovations at the Prospect Avenue, 53rd Street, and Bay Ridge Avenue stations on the BMT Fourth Avenue Line, was awarded on November 30, 2016[27] to Citnalta-Forte Joint Venture for $72 million, the first design–build contract in the subway system's history.[28] The station closed on June 5, 2017 for these renovations,[29][30][31] and reopened on November 2, 2017, a month ahead of schedule.[32]

The station's only fare controls are near the center of each platform, at the platform level.[45] Until the 2017 renovations,[46] they had their original trim line, colored brown with "P" at regular intervals, a bank of turnstiles, and token booth.[47] The Manhattan-bound side has two street stairs to the east sidewalk of Fourth Avenue, with one going to the southeastern corner of Prospect Avenue and Fourth Avenue, and the other going to the northeastern corner of 17th Street and Fourth Avenue. Meanwhile, the Bay Ridge-bound side has one to the northwestern corner of 17th Street and Fourth Avenue.[48][49] There are no crossovers or crossunders to allow free transfer between directions.[50][51]