If your ancestors, like several of mine, were early settlers of Cayuga County in Central ("Upstate") New York, it is important to understand the who, what, where, when, why and how the towns were established. This is an essential part of finding records about our ancestors and is likely to be the cause of some brick walls. Are you looking in a town that was called by another name at the time your ancestor lived there?
For example, ALL of central and western New York was considered Albany County until 1772, so if you're researching central New York ancestors who lived before 1772, look in Albany County's records.
In 1772, most of western New York became Tryon County, so if you're looking for records between 1772 and the 1780s, try looking in Tryon County's records. From there, more divisions took place.
In 1784 the name of Tryon County was changed to Montgomery County. Montgomery County was divided in 1788 to form Ontario County, and again in 1791 to form Herkimer County.
In 1794, Onondaga County was formed from Herkimer County and in 1799 Cayuga County was formed from Onondaga County.
In 1804 Seneca County was formed from part of Cayuga County, and in 1817 Tompkins County was created from southern portions of Cayuga and Seneca Counties. Furthermore, the townships within each county were divided.
Aurelius, once a township in Onondaga County, encompassing almost all of what today is the northern half of Cayuga County, now a much smaller township, covering less than 32 square miles. Originally the land was occupied by the Iroquois until in the Sullivan Expedition came through in 1779, destroying the region. It was first settled by European-Americans in 1789. Aurelius was later divided to form Auburn (1793), Brutus (1802), Weedsport (1802), Cayuga Village in modern-day Aurelius (1857), Sennett (1827), Fleming (1823), Owasco (1802), Mentz (incorporated as Jefferson in 1802 and name changed to Mentz in 1806), Montezuma (part of Mentz until 1859), Throop (part of Mentz, Aurelius and Sennett until 1859) and Ira (part of Mentz until 1821). Part of Mentz now called Port Byron, was called Bucksville until 1832. Port Byron was incorporated as a village in Mentz in 1837. Montezuma was part of the Cayuga Indian Reservation.
Cato was incorporated in 1802. Sterling, settled in 1805, was formed from part of Cato in 1812. (Fairhaven is a village in Sterling). Cato was further divided in 1821 when Conquest and Victory were formed. Meridian was incorporated as a village in Cato in 1854.
Genoa was settled in 1791 and was originally called Milton while it was still a part of Onondaga County. In 1802, Locke was formed from part of Genoa while it was still called Milton. In 1817, it was divided again, to form Lansing and Groton in Tompkins County. Summerhill was formed from Locke in 1831.
Scipio was settled in 1790 and incorporated in 1798. Scipio was divided in 1823 to form Venice and Ledyard. In 1823, parts of Aurelius and Scipio were taken, for the formation of Springport. Union Springs was set apart as a village in Springport in 1848 and Aurora was set apart as a village in Ledyard in 1837.
Sempronius was settled in 1793 and was incorporated about 1799. A portion of Sempronius was taken for Marcellus in Onondaga County. The region of Moravia was settled in 1789 and Niles in 1792. Both Moravia and Niles were officially incorporated in 1833.
This 1860 book "The Historical and Statistical Gazetteer of New York State", by John Homer French, gives a summary of each town's history. Following is the chapter on Cayuga County for quick reference:
You can find and read the entire book online for free at Archive.org.