William Henry Vanderbilt stated the line would not be as dark as the Metropolitan Railway (now part of the London Underground), and that there would be stations every eight blocks, or every .5 miles (0.80 km).
He stated that a private company would likely be needed to undertake the construction of the line, and would have to provide a sufficient bond to complete the work to protect the city against loss.
Though the Mayor in the message also suggested encouraging the New York Central Railroad to construct and operate a subway line, the company was unwilling to start such a venture.
Grant appointed a five-member Board of Rapid Transit Commissioners in April 1889 to lay out planned subway lines across the city.
The board released a plan for a mostly underground rapid transit line on October 20, 1891, and obtained consent from local authorities and the General Term of the New York Supreme Court.
[8] The act provided that the commission would lay out routes with the consent of property owners and local authorities, either build the system or sell a franchise for its construction, and lease it to a private operating company for fifty years.
It called for a subway line from New York City Hall in lower Manhattan to the Upper West Side, where two branches would lead north into the Bronx.
Then the line would diverge, with a western branch running under Broadway to Fort George before continuing via a viaduct over Ellwood Street and Kingsbridge Road to Bailey Avenue.
On August 19, 1901, E. P. Roberts and Terry & Tench Construction Company began work on Section 10, from Brook Avenue to Bronx Park and 182nd Street.
[24]: 191 The contractor for the subway purchased a large area of land on the Harlem River near 150th Street for the construction of a terminal for the East Side Line.
[32] On New Year's Day 1904, mayor George B. McClellan Jr. and a group of wealthy New Yorkers gathered at the City Hall station and traveled 6 miles (9.7 km) to 125th Street using handcars.
In February 1910, work began on the construction of a permanent terminal for the West Farms Branch at Zoological Park at 181st Street and Boston Road, replacing the temporary station at this location.
[57]: 105–106 To address overcrowding, the New York State Public Service Commission proposed to lengthen platforms to accommodate ten-car express and six-car local trains.
Local trains to the West Side Branch (242nd Street) ran from City Hall during rush hours and continued south at other times.
[71]: 3 Stations north of 96th Street and south of Brooklyn Bridge, which served both local and express trains, typically had two side platforms and two or three tracks.
Most stations in which the tracks were not under the middle of the street, with only a single platform under the sidewalks, were supplied with a pair of wide staircases due to their location in Harlem's business district.
[18]: 5 [69]: 10 [81]: 67 Architectural critic Christopher Gray wrote that "the stations were meant not only to appear sanitary and healthful but also to constitute a major public work like the automobile parkways of the 1920s".
[18]: 5 [69]: 10 Such plaques may have been installed to provide a visual aid to the large immigrant populations who were expected to ride the subway, many of whom did not read English,[83]: 46 [87]: 5347 although a writer for The New York Times said in 1957 that "non-English readers would have had to be rich in associative powers".
[88] Heins & LaFarge worked with the ceramic-producing firms Grueby Faience Company of Boston and Rookwood Pottery of Cincinnati to create the ceramic plaques.
The control houses were decorated with bricks, limestone, and terracotta, and contained details similar to the buildings at the Bronx Zoo's Astor Court, also designed by Heins & LaFarge.
[23]: 236, 256–257 In Murray Hill, the four-track line was divided into two double-track tunnels, providing space between the express tracks for a spur leading directly to the mainline railroad station at Grand Central Terminal.
This spur was never built, and the space was instead used to extend the IRT Lexington Avenue Line's express tracks northward as part of the Dual Contracts.
[23]: 236, 256–257 The Joralemon Street Tunnel under the East River, between the Bowling Green and Borough Hall stations, was dug as a pair of cast iron tubes.
[100]: 329 From the main powerhouse, 11,000 volts of alternating current passed through high tension feeder cables that ran under 58th Street eastward to the subway tunnel under Broadway, and were then carried through ducts to the substations.
[101] The original subway cars, designed with two doors at the ends of each side, were inefficient, causing delays of up to fifty seconds during rush hours.
Consulting engineer Bion J. Arnold wrote in 1908 that "the number of patrons is increasing yearly and the maximum carrying capacity is therefore taxed to the utmost limit".
While high-end retailers and middle-class department stores were moving northward at the beginning of the 20th century, they chose to remain further west on Sixth and Fifth Avenues.
The subway's opening brought about an increase in land values around it, as apartment buildings of over 10 stories and smaller business structures were erected on Broadway.
[53]: 185–186 Further north, around the West Side Branch in Morningside Heights, developers started constructing middle-class apartment buildings when the subway opened.
[107] Around the East Side Branch in central Harlem, commercial developments such as theaters and banks moved to Lenox Avenue, under which the subway ran.