Forty Big Apple landmarks, from Coney Island to City Island, from a swimming pool to a cemetery, are competing for $3 million in preservation funds — with the public deciding the winners by online votes.

The competition, sponsored by Partners in Preservation, a collaboration between American Express and the National Trust for Historic Preservation, allows voting through May 21.

Mayor Bloomberg said the grants will “help save the places that matter to people.’’

Votes can be cast at http://www.partnersinpreservation.com or www .facebook.com/partnersinpreservation.