Peconic County, New York
Peconic County ( //) is a proposed new county on Long Island in New York that would secede the five easternmost towns of Suffolk County: East Hampton, Riverhead, Shelter Island, Southampton and Southold, plus the Shinnecock Indian Reservation.
Peconic County has been discussed for more than 50 years – ever since Suffolk County moved its offices from the official county seat in Riverhead 32 miles west to Hauppauge, New York, in more densely populated western Suffolk County. 
The big drive for the county was a difference in character between western Suffolk County which is predominantly a New York City bedroom community while the east end (or " East End") is dominated by home owners who want to preserve the area's more rural and upscale character.
In 1997, 71 percent of the east end voters approved a nonbinding resolution to secede. However, the New York State Assembly has never approved the enabling legislation. East End newspapers speculated that the Assembly was afraid that it would encourage a wave of secessions in the state including Staten Island seceding from New York City  and perhaps even causing the division of upstate and downstate New York.
The secession movement has not been active in recent years.
At the 2010 census, the five towns and the Shinnecock Reservation had a land area of 900.581 km² (347.72 mi²), or about 38.12 percent of Suffolk County's land area. Its total population was 136,775 inhabitants, or about 9.16 percent of the county's population. Its average population density was 151.87 km² (393.35 mi²).  If the proposed secession were to occur, the surviving Suffolk County would have a land area of 1,462.001 km² (564.482 mi²) and an adjusted 2010 census population of 1,356,575 inhabitants. It would be left with a population density of 927.90/km² (2,403.22 mi²). As can be seen, the western part of Suffolk has more than six times the population density of its eastern neighbor.
- Adirondack County - another proposed county in New York
- Brookhaven County - an adjacent proposed county in New York made from the Town of Brookhaven.