The Landmarks Law requires that, to be designated, a potential landmark must be at least 30 years old and must possess "a special character or special historical or aesthetic interest or value as part of the development, heritage, or cultural characteristics of the city, state, or nation".

There are four types of landmarks:

1. Individual Landmarks (individual structures that can range from bridges to rowhouses to skyscrapers; examples include the Woolworth Building, the Langston Hughes House in Harlem, and the Wonder Wheel at Coney Island);
2. Interior Landmarks (building interiors that are “customarily open or accessible to the public,” such as the Marine Air Terminal at LaGuardia Airport, the RCA Building Lobby, and the Ed Sullivan Theater);
3. Scenic Landmarks (city-owned parks or other landscape features, such as Prospect Park, Central Park, and Ocean Parkway); and
4. Historic Districts (areas of the city that possess architectural and historical significance and a distinct "sense of place," such as Ladies' Mile in Manhattan, Cobble Hill in Brooklyn, and St. George-New Brighton in Staten Island).

The LPC receives a steady stream of suggestions for designation from interested citizens, property owners, community groups, public officials, and others.

Landmarks Commissioners and staff also may identify potential buildings and areas of interest. The Commission asks members of the public who propose properties for potential designation to fill out a Request for Evaluation (RFE) form. This form requests the individual to provide as much information about the property as possible, including photographs and/or slides.