The largest abandoned subway tunnel in the United States Is located in which city?

In 1928, the construction of the underground rapid transit train system in Cincinnati was indefinitely cancelled; to date, there are no concrete plans to revive the project. Rapid transit was seen as the solution for downtown congestion during the first quarter of the 20th century. Six million dollars were allocated for the project, but construction was delayed due to World War I. Unexpected post-war inflation doubled the cost of construction, so the project could not be finished at the original estimated price. Various attempts to use the subway tunnels for mass transit have been unsuccessful. Political squabbling, the Great Depression, World War II, and the rise in popularity of the automobile have contributed to the failure of the proposals. Today, many Cincinnatians are unaware of the tunnels underneath them.