St. Lawrence County is a county in the U.S. state of New York. As of the 2020 census, the population was 108,505. The county seat is Canton. The county is named for the Saint Lawrence River. This was as named by early French explorer Jacques Cartier for the Christian saint Lawrence of Rome, as he visited the river on the saint's feast day. The county is part of the North Country region of the state.

St. Lawrence County comprises the Ogdensburg-Massena, NY Micropolitan Statistical Area and is New York's largest county by area.

When counties were established by England in the Province of New York in 1683, the present St. Lawrence County was part of Albany County. This was an enormous territory, including the northern part of New York State as well as all of the present State of Vermont and, in theory, extending westward to the Pacific Ocean. The county was reduced in size on July 3, 1766, by the creation of Cumberland County, and further on March 16, 1770, by the creation of Gloucester County, both containing territory now in Vermont.

On March 12, 1772, what was left of Albany County was split into three parts, one remaining under the name Albany County. The other two were called Tryon County (later renamed Montgomery County) and Charlotte County (later renamed Washington County).

Tryon County contained the western portion (and, since no western boundary was specified, theoretically extended west to the Pacific). The eastern boundary of Tryon County was approximately five miles west of the present city of Schenectady, and the county included the western part of the Adirondack Mountains and the area west of the West Branch of the Delaware River. The area then designated as Tryon County included what are now 37 counties of New York State. The county was named for William Tryon, colonial governor of New York. Charlotte County contained the eastern portion of Albany County.

In 1784, following the peace treaty that ended the American Revolutionary War, the name "Charlotte County" was changed to Washington County to honor George Washington, the American Revolutionary War general and later President of the United States of America. Tryon County was changed to Montgomery County to honor the general, Richard Montgomery, who had captured several places in Canada and died trying to capture the city of Quebec. It replaced the name of the British governor, hated by the rebels.

In 1788, Clinton County was split off from Washington County. This was a much larger area than the present Clinton County, including part of what would later become St. Lawrence County, as well as several other counties or county parts of the present New York State.

In 1789, the size of Montgomery County was reduced by the splitting off of Ontario County from Montgomery. The actual area split off from Montgomery County was much larger than the present county, also including the present Allegany, Cattaraugus, Chautauqua, Erie, Genesee, Livingston, Monroe, Niagara, Orleans, Steuben, Wyoming, Yates, and part of Schuyler and Wayne Counties.

St. Lawrence County is part of Macomb's Purchase of 1791.

In 1791, Herkimer County was one of three counties split off from Montgomery (the other two being Otsego, and Tioga County). This was much larger than the present county, however, and was reduced by a number of subsequent splits. The first was the splitting off in 1794 of Onondaga County. This county was larger than the current Onondaga County, including the present Cayuga, Cortland, and part of Oswego Counties. This was followed by the splitting off in 1798 from Herkimer County of two portions: one, Oneida County, was larger than the current Oneida County, including the present Jefferson, Lewis, and part of Oswego Counties; another portion, together with a portion of Tioga County, was taken to form Chenango County.

In 1799, Clinton County was reduced in size by the splitting off of Essex County from Clinton County.

In 1802, parts of Clinton, Herkimer, and Montgomery counties were taken to form the new St. Lawrence County. At that time Ogdensburg was the county seat. In 1828 the county seat was moved to Canton. The selection of Canton as the county seat was a compromise by the state legislature to end competition between factions supporting Ogdensburg and Potsdam for the county seat.

On September 5, 1944, a 5.8 magnitude earthquake centered in Massena struck the county. The earthquake was felt from Canada to Maryland, and from Maine to Indiana. The earthquake was the strongest earthquake in New York State history.

According to the United States Census Bureau, the county has a total area of 2,821 square miles (7,310 km), of which 2,680 square miles (6,900 km) is land and 141 square miles (370 km) (5.0%) is water.

It is the largest county by area in the state of New York. It is larger than either of the states of Rhode Island (1544.9 square miles) or the state of Delaware (2488.72 square miles). St. Lawrence County is part of the North Country region.

Part of the county is in the Adirondack Park. It includes much of the Oswegatchie River, Cranberry Lake and Lake Ozonia.

The Port of Ogdensburg in St. Lawrence County is the only U.S. port on the St. Lawrence Seaway. This waterway allows ships and vessels to pass through the St. Lawrence River and on to the Great Lakes. Ogdensburg Harbor Light is listed in the National Register of Historic Places, and in the National Register of Historic Places listings in St. Lawrence County, New York

• Stormont, Dundas and Glengarry United Counties, Ontario, Canada – north
• Leeds and Grenville United Counties, Ontario, Canada – northwest
• Franklin County – east
• Herkimer County – south
• Hamilton County – south
• Lewis County – southwest
• Jefferson County – west

Historical population

Census	Pop.	Note	%±
1810	7,885		—
1820	16,037		103.4%
1830	36,354		126.7%
1840	56,706		56.0%
1850	68,617		21.0%
1860	83,689		22.0%
1870	84,826		1.4%
1880	85,997		1.4%
1890	85,048		−1.1%
1900	89,083		4.7%
1910	89,005		−0.1%
1920	88,121		−1.0%
1930	90,960		3.2%
1940	91,098		0.2%
1950	98,897		8.6%
1960	111,239		12.5%
1970	111,991		0.7%
1980	114,254		2.0%
1990	111,974		−2.0%
2000	111,931		0.0%
2010	111,944		0.0%
2020	108,505		−3.1%
U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010–2020

As of the census of 2000, there were 113,931 people, 40,506 households, and 26,936 families residing in the county. The population density was 42 inhabitants per square mile (16/km). There were 49,721 housing units at an average density of 18 units per square mile (6.9/km). The racial makeup of the county was 94.51% White, 2.38% African American, 0.87% Native American, 0.71% Asian, 0.03% Pacific Islander, 0.69% from other races, and 0.51% from two or more races. Hispanic or Latino of any race were 1.79% of the population. 16.9% were of French, 16.1% Irish, 13.9% American, 11.6% English, 8.1% French Canadian, 7.9% German and 7.6% Italian ancestry according to Census 2000. 95.6% spoke only English, while 3.2% spoke French and 1.2% Spanish at home.

There were 40,506 households, out of which 31.80% had children under the age of 18 living with them, 51.50% were married couples living together, 10.30% had a female householder with no husband present, and 33.50% were non-families. 26.50% of all households were made up of individuals, and 11.20% had someone living alone who was 65 years of age or older. The average household size was 2.49 and the average family size was 2.99.

In the county, the population was spread out, with 23.40% under the age of 18, 13.80% from 18 to 24, 27.40% from 25 to 44, 22.40% from 45 to 64, and 13.00% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 103.30 males. For every 100 females age 18 and over, there were 102.10 males.

The median income for a household in the county was $30,356, and the median income for a family was $34,510. Males had a median income of $30,135 versus $24,253 for females. The per capita income for the county was $14,728. About 12.30% of families and 19.90% of the population were below the poverty line, including 21.30% of those under age 18 and 10.30% of those age 65 or over.

St. Lawrence County Racial Composition

Race	Num.	Perc.
White (NH)	96,556	90%
Black or African American (NH)	2,788	3%
Native American (NH)	1,143	1.1%
Asian (NH)	1,089	1%
Pacific Islander (NH)	19	0.01%
Other/Mixed (NH)	4,078	4%
Hispanic or Latino	2,832	2.61%

There are 17 school districts with territory in St. Lawrence County. 17 of those centered in the county are under the jurisdiction of the St. Lawrence-Lewis BOCES Supervisory District along with Harrisville Central School District in Lewis County, New York.

• Brasher Falls Central School District: St. Lawrence Central School, Brasher Falls
• Canton Central School District: Hugh Williams Senior High School, Canton
• Clifton-Fine Central School District: Clifton-Fine Central School, Star Lake
• Colton-Pierrepont Central School District: Colton-Pierrepont Central School, Colton
• Edwards-Knox Central School District: Edwards-Knox Central School, Russell
• Gouverneur Central School District: Gouverneur Junior/Senior High School, Gouverneur
• Hammond Central School District: Hammond Central School, Hammond
• Hermon-Dekalb Central School District: Hermon-Dekalb Central School, Dekalb Junction
• Heuvelton Central School District: Heuvelton Central School, Heuvelton
• Lisbon Central School District: Lisbon Central School, Lisbon
• Madrid-Waddington Central School District: Madrid-Waddington Central School, Madrid
• Massena Central School District: Massena Senior High School, Massena
• Morristown Central School District: Morristown Central School, Morristown
• Norwood-Norfolk Central School District: Norwood-Norfolk Central School, Norfolk
• Ogdensburg City School District: Ogdensburg Free Academy, Ogdensburg
• Parishville-Hopkinton Central School District: Parishville-Hopkinton Central School, Parishville
• Potsdam Central School District: Potsdam High School, Potsdam

Other school districts with territory in the county include:

All public high schools in St. Lawrence County compete in the New York State Public High School Athletic Association Section X Northern Athletic Conference.

Saint Lawrence County is home to St. Lawrence University, State University of New York at Potsdam, Clarkson University, the SUNY-ESF Ranger School, and the State University of New York at Canton.

United States presidential election results for St. Lawrence County, New York

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2020	24,608	54.80%	19,361	43.11%	938	2.09%
2016	19,942	50.93%	16,488	42.11%	2,728	6.97%
2012	15,138	40.70%	21,353	57.41%	700	1.88%
2008	16,956	41.03%	23,706	57.36%	664	1.61%
2004	18,029	43.17%	22,857	54.73%	875	2.10%
2000	16,449	41.34%	21,386	53.75%	1,951	4.90%
1996	10,827	28.14%	21,798	56.65%	5,852	15.21%
1992	13,901	32.85%	18,197	43.00%	10,219	24.15%
1988	20,290	51.39%	18,921	47.92%	270	0.68%
1984	26,062	61.83%	15,963	37.87%	124	0.29%
1980	18,437	46.53%	17,006	42.92%	4,181	10.55%
1976	22,249	55.71%	17,503	43.83%	182	0.46%
1972	26,145	63.00%	15,286	36.83%	72	0.17%
1968	20,982	55.31%	15,662	41.29%	1,289	3.40%
1964	12,102	29.30%	29,173	70.62%	32	0.08%
1960	25,848	57.06%	19,430	42.89%	24	0.05%
1956	31,897	74.54%	10,892	25.46%	0	0.00%
1952	28,036	68.27%	13,000	31.65%	32	0.08%
1948	21,160	60.59%	13,200	37.80%	565	1.62%
1944	21,919	58.89%	15,223	40.90%	77	0.21%
1940	24,339	60.86%	15,569	38.93%	82	0.21%
1936	26,031	65.81%	12,763	32.27%	762	1.93%
1932	22,650	63.48%	12,687	35.56%	343	0.96%
1928	25,804	66.23%	12,567	32.26%	589	1.51%
1924	22,583	71.50%	7,103	22.49%	1,898	6.01%
1920	24,651	75.60%	7,213	22.12%	742	2.28%
1916	13,142	66.77%	6,056	30.77%	485	2.46%
1912	8,404	44.98%	5,329	28.52%	4,952	26.50%
1908	14,151	67.87%	5,898	28.29%	800	3.84%
1904	15,274	70.43%	5,798	26.74%	614	2.83%
1900	15,296	71.02%	5,699	26.46%	544	2.53%
1896	15,287	70.97%	5,749	26.69%	505	2.34%
1892	13,177	64.17%	6,156	29.98%	1,202	5.85%
1888	14,611	67.56%	6,509	30.10%	508	2.35%
1884	13,441	67.86%	6,035	30.47%	331	1.67%

Prior to the 1992 presidential election, St. Lawrence County was a traditionally Republican county, supporting the Democrats only in their sweep of New York State counties in 1964. From 1992 through the 2012 election, St. Lawrence County swung Democratic, posting double-digit victories for Democratic candidates, most notably in 1996 when Bill Clinton won the county by 28-point margin over Bob Dole. The first Republican victory in the county since 1988 came in 2016 when Donald Trump carried the county by an eight-point margin. In 2020, it was one of only a few counties in Upstate New York where Trump improved his margin, this time carrying it by over 10 points.

• 1340 WMSA, Massena
• WVLF-FM Mix 96.1
• WRCD-FM 101.5 The Fox
• WSNN (99.3, Potsdam)
• WPDM (1470, Potsdam)
• WSLU (89.5, Canton)

The following public use airports are located in the county:

• Massena International Airport (MSS) – Massena
• Ogdensburg International Airport (OGS) – Ogdensburg
• Potsdam Municipal Airport (PTD) – Potsdam
• Moores Airport (1E8) – Degrasse

#	Location	Population	Type	Area
1	‡Akwasasne	About 12,000	CDP/Reservation	Riverside
2	Massena	10,883	Village	Riverside
3	Ogdensburg	10,436	City	Riverside
4	Potsdam	9,428	Village	East
5	†Canton	6,314	Village	Center
6	Gouverneur	3,949	Village	Riverside
7	Norwood	1,560	Village	Riverside
8	Norfolk	1,327	CDP	Riverside
9	Hannawa Falls	1,042	CDP	East
10	Waddington	972	Village	Riverside
11	Star Lake	809	CDP	South
12	Madrid	757	CDP	Riverside
13	Heuvelton	714	Village	Riverside
14	Brasher Falls	669	CDP	East
15	Parishville	647	CDP	East
16	Hailesboro	624	CDP	South
17	DeKalb Junction	519	CDP	East
18	Winthrop	510	CDP	East
19	Edwards	439	CDP	South
20	Hermon	422	CDP	Center
21	Morristown	395	CDP	Riverside
22	Colton	345	CDP	East
23	Rensselaer Falls	332	Village	Riverside
24	Richville	323	Village	South
25	Hammond	280	Village	Riverside
26	Cranberry Lake	200	CDP	Southeast

† - County Seat

‡ - Not Wholly in this County

• List of counties in New York
• National Register of Historic Places listings in St. Lawrence County, New York
• St. Lawrence County Public Transportation

• St. Lawrence County webpage Archived November 19, 2016, at the Wayback Machine
• St. Lawrence County History pages

• Sullivan, James; Williams, Melvin E.; Conklin, Edwin P.; Fitzpatrick, Benedict, eds. (1927), "Chapter III. St. Lawrence County.", History of New York State, 1523–1927 (PDF), vol. 2, New York City, Chicago: Lewis Historical Publishing Co., p. 519-23, hdl:2027/mdp.39015019994048, Wikidata Q114149636

44°30′N 75°04′W / 44.50°N 75.07°W / 44.50; -75.07