Sea Isle City is a city in Cape May County, New Jersey, United States. It is part of the Ocean City Metropolitan Statistical Area. As of the United States 2000 Census, the city population was 2,835. Sea Isle City is located on Ludlam Island, which also contains part of Dennis Township. Sea Isle City was originally incorporated as a borough on May 22, 1882, from portions of Dennis Township, based on the results of a referendum held six days earlier. The borough was reincorporated on March 31, 1890. On April 30, 1907, the area was reincorporated as the City of Sea Isle City, based on the results of a referendum held on April 20, 1907.