The Ontario County Municipal Building is located at 20 Ontario Street, Canandaigua NY 14424; phone: 585‑396‑4274.
The Seneca Indians were the original occupants and owners of Ontario County. The Senecas called themselves "Nun-da-wa-o-no" which signifies "the great hill people." This was the name of their oldest village, situated upon a hill near the head of Canandaigua Lake, where according to Seneca tradition, the tribe originated by springing from the ground.
In 1787 Phelps and Gorham became the owners of a vast tract of land in Montgomery County, located west of Seneca Lake, in extent being about 2,600,000 acres. The greater part of the remainder of the State west of the purchase just mentioned soon afterward became the property of the so-called Holland Land Company. The proprietary of each of these tracts at once began its development by making surveys and settlements thereon. The permanent settlement on the Phelps and Gorham tract began in 1787, and increased so rapidly that in 1789 it was deemed advisable to make a division of Montgomery county. Therefore, upon the presentation of an application, the Legislature, on January 27, passed an act creating Ontario county, and including within its boundaries all the lands of the State west of Seneca Lake, or in other words, the whole tract which was ceded by New York to Massachusetts west of the pre-emption line. The county was named from Lake Ontario, which formed its original northern boundary. The effective part of the act creating the county reads as follows: "Whereas, the county of Montgomery is so extensive as to be inconvenient to those who now are, or may hereafter settle in the western part of that county; Therefore, be it enacted, etc., That all that part of the county of Montgomery which lies to the westward of a line drawn due north to Lake Ontario from the mile-stone or monument marked eighty-two, and standing on the line of division between this State and the Commonwealth of Pennsylvania, shall be one separate and distinct county, and called and known by the name of Ontario."
The third section of the act provided that until other legislation should be had in the premises it " shall be lawful for the justices of the Court of Sessions for the said county of Ontario to divide the said county into two or more districts, as they shall deem expedient and convenient to the inhabitants." It was under the provisions of this act that the original districts of Bristol, Canandaigua, Bloomfield, Farmington, Gorham, and Middletown (Naples) were formed, each thus comprising a much larger area of territory than at present.
At the time of the organization of the county the total population of its towns or districts did not exceed 1,000 persons, as the first federal census, made soon afterward, gave the county a total of 205 families and 1081 inhabitants.
After the erection of the county, to complete the organization, the following officials were appointed : Oliver Phelps, judge of the Common Pleas; John Cooper, surrogate; and Nathaniel Gorham, county clerk. The first sheriff of the county, Judah Colt, was not appointed to office until April 7, 1790.
As is well known, the county seat and buildings have been located at Canandaigua since the erection of the county; and while the people of Geneva had a strong desire to possess the county properties, even at the time the county was formed, their claims were not well grounded, inasmuch as there was then a doubt whether the locality of that village was on the Phelps and Gorham tract, or on the lands claimed by the lessees. Furthermore, the seat of operations of the proprietors had, by 1789, been removed from Geneva to Canandaigua, and as those proprietors were chiefly instrumental in causing the division of the mother county — Montgomery — it was only natural that the same influences should control the location of the county buildings. Therefore, the commissioners appointed to examine the several localities desirable for the seat of justice, had no difficulty in designating Canandaigua as the place most suitable.