The Beach Pneumatic Transit was an early technology demonstrator for underground public transit in New York City. Running on pneumatic power, it was built by Alfred Ely Beach between 1869 and early 1870. The original terminus resided in the basement of the Rogers Peet Building in Lower Manhattan, near the old City Hall station. A one-car shuttle carried riders between the building and a dead end approximately 300 feet (91 m) away. Despite ambitious plans to construct stations along a five-mile route to Central Park, the project never expanded beyond the short demonstration track and closed in 1873.

Alfred Ely Beach demonstrated a model of basic pneumatic subway system, in which air pressure in the tube pushed the cars, at the American Institute Exhibition in New York in 1867. After demonstrating that the model was viable, in 1869 Beach and his Beach Pneumatic Transit Company began constructing a pneumatically powered subway line beneath Broadway. Funneled through a company he set up, Beach put up $350,000 ($8.47 million in 2025) of his own money to pay for the full-scale test project. Built with a tunneling shield, the tunnel was complete in only 58 days. Its single tunnel, 300 feet (90 m) long, 8 feet (2.4 m) in diameter, was completed in 1870 and ran under Broadway from Warren Street to Murray Street.

However, one of the city's top politicians of the day, William "Boss" Tweed, refused to support the project. With no initial political support for the project, Beach started the project by claiming he was building postal tubes. The initial permit was to install a pair of smaller postal tubes below Broadway; however, Tweed later amended the permit to allow the excavation of a single large tunnel, wherein the smaller tubes could reside.

The exact location of the tubes was determined during construction by compass and survey as well as verified by driving jointed rods of iron up through the roof of the tunnel to the pavement. The line was built as a demonstration of a pneumatic transit system, open to the public with a 25-cent fare per person. Proceeds for the admission went to the Union Home and School for Soldiers' and Sailors' Orphans. It was planned to run about 5 miles (8 km) in total, to Central Park, if it were ever completed.

For the public, the project was used as an attraction. It ran only a single car on its one-block-long track to a dead-end at its terminus, and passengers would simply ride out and back, to see what the proposed subway might be like. During its first two weeks of operation, the Beach Pneumatic Transit sold over 11,000 rides, and over 400,000 total rides in its single year of operation.

Although the public showed initial approval, Beach was delayed in getting permission to expand it due to official obstruction for various reasons. By the time he finally gained permission in 1873, public and financial support had waned, and the subway was closed down within the year. The project was shut down when a stock market crash caused investors to withdraw support. It is unclear that such a system could have been practical for a large-scale subway network.

After the project was shut down, the tunnel entrance was sealed. The station, built in part of the basement of the Rogers Peet Building, was reclaimed for other uses until the entire building was lost to fire in 1898. In 1912, workers excavating for the BMT Broadway Line (serving the present-day N, ​R, and ​W trains) dug into the old Beach tunnel, where they found the remains of the car, the tunnelling shield used during initial construction, and even the piano in the subway's waiting room. The shield was removed and donated to Cornell University, which has since lost track of its whereabouts.

The tunnel was almost completely within the limits of the Broadway Line's City Hall station, near the old City Hall station, but it is rumored that a small portion could still be accessed by a manhole on Reade Street. The New-York Historical Society commissioned a plaque honoring Alfred Beach to be placed in the City Hall station.