Canton became the County seat as a compromise site. That Canton has a courthouse is a tribute to its tenacity after two fires tried to destroy the entire complex. Canton, itself, had only been born when, on March 6, 1801, a petition was addressed to the state legislature bearing the signatures or the "x" marks of more than a hundred pioneers asking that the ten townships then in existence be incorporated into one town by the name of Lisbon and be attached to Clinton County.

The legislature granted the request and Lisbon elected a full set of officers but whenever it became necessary for any of the hardy pioneers to go to court or to transact business on a county basis it involved a long and difficult trek to Plattsburgh. A new petition, signed by 156 names, was then sent to the legislature on February 8, 1802, asking that the territory involving the former ten townships be set off as a county to be called St. Lawrence. The petition also suggested that one of the old stone buildings of the Oswegatchie Fort be used as a courthouse, jail and county clerk's office until the county could erect suitable buildings of its own.

The legislature granted the request of the petitioners on March 3, 1802, and the county was created. As the county's business grew, the Court of Common Pleas and General Sessions moved into the old Oswegatchie barracks, which, by an act of law, became the "courthouse". During the war of 1812, the British took several pot shots, by land and by sea, at the "courthouse" and did considerable damage but when, in 1814 the county prepared to repair the damage, many landed proprietors and settlers in the central part of the county, including Canton, urged that a more central location "less exposed to the hostile incursions in case of war," be chosen. Ogdensburg fought to keep its courthouse and promised to spend $2,000 on new roads to make it easier to get there. Potsdam staged a big campaign to win the courthouse for itself. Nathan Ford, who had been the founder of Ogdensburg, fought hard to keep the courthouse there but when his health failed, his cause failed with him. When the question of a relocation of the county courthouse reached the legislature, a suggestion was made that the issue be settled by a plebiscite. A vote was taken, in 1827, and turned out to be: 4,542 in favor of the removal of the courthouse to a more central location and 3,757 against.

When the legislature, acting on the result of that poll, got around to enacting a law, on January 28, 1828, authorizing a new location for the county buildings, the Senate in Albany designated neither Ogdensburg nor Potsdam, but Canton. That first Canton courthouse, the county's second, was built on the site of today's county buildings. It was of the classic Grecian style with four high pillars across the front and a steeple rising out of the middle of the roof. Two stories high, forty by forty-four feet, it housed only the courts in four rooms downstairs and in a single courtroom occupying the whole of the second floor. Separate buildings were built for the jail and clerk's office, but the planners had not anticipated the county's growth and both the courthouse and the jail had to be enlarged in 1850.

The courthouse caught fire about 2 o'clock in the morning of February 21, 1893, and burned out completely, leaving only the four bare walls standing. At first the reports stated the fires started from some unknown cause, but later on, the fact of careless smoking was reported to be the reason for the fires. In the complete destruction of this original courthouse, the roster with paperwork of the current county court cases at that time was lost -- how could trials take place? Even before the temporary quarters were found, it was obvious that prisoners being held for trial might have to be released. Bailiffs and the sheriff had been able to save a few chairs and 274 law library books belonging to the Bar. Even the minutes of the grand jury had gone up in smoke, and only one indictment had been saved, all because that defendant had no lawyer and the paperwork had gone into the clerk's pocket!

However, county Judge Kellogg at the county clerk's office next door consulted law books and soon declared that county court would convene at Canton's town hall, that prisoners awaiting trial would be detained unless on bail. As soon as news of the disaster spread, old envies and hopes were reborn and citizens of Norwood, Potsdam, Gouverneur and Ogdensburg sent delegations to offer "temporary" court houses and during the next months a committee visited other county courthouses for ideas. None would have the beauty of the Potsdam sandstone and Gouverneur stone that would be finally used. Canton won its battle and on July 11, 1893, the county board appointed Evans and Ackerman of Binghamton, as architects to design it and appropriated $60,000 to build the new courthouse, in the Romanesque style. The foundation walls were laid with granite five feet thick, the corners, windows and coping were of Norwood black limestone and light grey Gouverneur granite was used in the walls. Having learned a lesson by the loss of all the court records in the fire, the annex was made fireproof, with iron doors in the passages.

In 1923 an addition was added to the left for the county clerk's office. The curved wall at the right was expanded and the tower was redesigned in the reconstruction of the building. That proved to be a false security, however, and for the second time the courthouse side was gutted by fire, at night in January 1925.

The county supervisors had, providentially, increased the amount of insurance carried on the building only a few weeks before. That policy brought the county enough funds to build a new interior inside the stone walls without changing the appearance of the building and without any new cost to the taxpayers. The contracting firm of Munn and Shea of Montreal (Samuel C.P. Williams, architect) at a cost of $226,360, was hired with the policy covering most of the cost. In its rebuilding , it was again made as fireproof as possible with the only wood used in its reconstruction being the balustrade of the staircase. The building is constructed of native limestone and trimmed with red Potsdam sandstone all laid in what is known as broken ashlar pattern. Much strength and ruggedness is evident, with some stone supporting walls nearly four feet thick. The roof is of copper with the stone tower rising well above. The corridor walls are of glazed tile with quarry stone tile on the floors. The top floor in addition to a courtroom of 48 x 65 feet and seating 200 persons, holds a dual set of jury rooms, a Judge's chambers, numerous conference rooms and a law library. In 1957 another addition was erected, to house the District Attorney's quarters, Family Court and offices.

The latest addition occurred in the early 1990's with another building [the new courts building] erected to the left of the main county building.