Several skyscrapers are located on 23rd Street, including the Flatiron Building, the Metropolitan Life Insurance Company Tower, and One Madison.

[12] In 1907, a small lot of land on the north side of 23rd Street, between Twelfth and Eleventh Avenues, was acquired by the Commissioner of Docks and Ferries.

In 2000, the westernmost block of 23rd Street was demolished as part of a reorganization of traffic patterns and an expansion of the park.

[13] The expanded 2.5-acre (1.0 ha) park contains a dog run, children's playground, basketball court, and soccer green.

[15] On the north side of 23rd Street, just west of the High Line, is "HL23", a residential building that hangs over the narrow linear park.

[19][20] The Hotel Chelsea, New York City's first co-op apartment complex, was built at 222 West 23rd Street in 1883.

The tallest of these is the 700-foot (210 m) Metropolitan Life Insurance Company Tower, built in 1909 at the intersection of 24th Street and Madison Avenue.

[35] A large hospital run by the Veterans Health Administration, the Manhattan Campus of the VA NY Harbor Healthcare System, is located at 423 East 23rd Street, near the northeast corner of the intersection with First Avenue.

[37] Built at the beginning of the 20th century, the baths were named after Asser Levy, one of the city's first Jewish settlers.

Stretching south to 18th Street, the 2-acre (0.81 ha) public space is built on the site of a concrete plant and parking lot.

[42][43] The seaplane base, which is part of a marina, also contains a parking lot whose entrance and exit is located at the eastern end of 23rd Street.

Peter Cooper Village was a sister project to MetLife's Stuyvesant Town, which was built across 20th Street to the south.

Instead, the area was to be used as an open space for military training,[47] as well as an assembly point in the event the city was invaded.

[49][50][51] By 1847, the open area was 7 acres (2.8 ha), comprising the land of the current Madison Square Park.

[59] The growth of interstate trucking during the 1950s led to a drop in rail traffic throughout the United States,[60] and the viaduct was effectively abandoned in 1980.

[71] During the 1870s, the Sixth Avenue Elevated was built,[72] significantly increasing the number of customers who shopped at stores along the route.

[79][80] In 1869, Pavonia Ferry opened a terminal on the shore of the Hudson River at Pier 63, which aligned with the western end of 23rd Street.

[82] In the late 1980s, boat enthusiast John Krevey converted an old railroad barge on the Hudson River to a floating jetty called Pier 63.

The lightship Frying Pan and the fire vessel John J. Harvey were also originally moored to Pier 63,[84] with both listed on the National Register of Historic Places.

[86] On January 1, 1825, the New York House of Refuge, a jail for juvenile delinquents, opened on Broadway between 22nd and 23rd Streets.

[96] When the Prince of Wales, Edward VII, visited the hotel in 1860, the commercial appeal of the adjacent neighborhood was greatly increased.

[98] The National Academy of Design building opened in 1863 at the intersection of 23rd Street and Fourth (now Park) Avenue.

[102] The building, designed by Henry Fernbach, was massive by contemporary standards, standing seven stories high and measuring 200 feet (61 m) wide.

By 1876, there were so many brothels in the area bounded by 23rd and 57th Streets, between Fifth and Seventh Avenues, that New York City Police Department captain Alexander S. Williams nicknamed this strip of land "Tenderloin".

[107] Referring to the increased number of bribes he would receive for police protection of both legitimate and illegitimate businesses there – especially the many brothels – Williams said, "I've been having chuck steak ever since I've been on the force, and now I'm going to have a bit of tenderloin.

[119] Baruch College, an institution within the City University of New York system, was a successor to the Free Academy.

[120] Founded by businessman and City College alumnus Bernard Baruch,[121] the campus includes the Lawrence and Eris Field Building at the southeast corner of Lexington Avenue and 23rd Street in Gramercy.

[126] On October 17, 1966, the street was the location of New York's deadliest fire until the September 11 attacks, in terms of firefighters killed.

One 2,500-square-foot (230 m2) office space between Park and Lexington Avenues was leased for $240,000 per year in March 2017,[139] while a 1,000-square-foot (93 m2) apartment three blocks east was being sold for $1 million.

[142][143] In 2003, the Straphangers Campaign listed the M23 as one of the slowest in the city, winning its "Pokey Award" for going at an average speed of 3.7 miles per hour (6.0 km/h).