There have been 66 counties in New York State and here is their "genealogy":
There are currently 62 counties in New York State.Five of these counties are the vestigial counties that make up New York City, leaving 57 real counties.In addition, there were 4 counties that used to be in New York State and are now part of Massachusetts and Vermont.Thus, New York State had 66 counties between November 1, 1683 when the first 12 counties were organized and today.
.The Genealogy of the Counties of New York State:
Any errors in the spelling of the counties of New York or mistyping of the years they were established are solely mine and I would appreciate any corrections to be eMailed to me.
1.Portions of Westchester County were annexed by New York County in 1873 and 1895. 2.Transferred to Massachusetts on October 7, 1691. 3.Transferred to Vermont in 1790. 4.Transferred to Massachusetts on October 7, 1691. 5.Transferred to Vermont in 1790. 6.As Tryon; changed April 2, 1784. 7.Parts of Montgomery, Herkimer and Oneida, provisionally annexed. 8.As Charlotte; changed April 2, 1784.Also, parts transferred to Vermont in 1790.
Source:Local Government Handbook, Division of Local Government Services, NYS Department of State, 4th Edition, 1987.
I hope this information is useful or, at least, interesting.