Collin County Texas map
33.19° N · 96.58° W · County seat: McKinney · 886 sq mi · Central Time
Collin County grew from farmland to more than a million people in two generations, and it is still the fastest-growing large county in Texas: 1,064,465 at the 2020 census, an estimated 1,254,658 by 2024. The growth follows three corridors north out of Dallas — US-75, the Dallas North Tollway and SH-121.
McKinney sits at the center. Plano and Frisco fill the southwest corner; Lavon Lake takes up the southeast.
Where Collin County is
The county was cut out of Fannin County in 1846 and named for Collin McKinney, one of the authors of the Texas Declaration of Independence and the oldest man to sign it — the county seat carries his surname and the county his given name, which is unusual in Texas.
It borders Grayson on the north, Fannin on the northeast, Hunt on the east, Rockwall on the southeast, Dallas on the south and Denton on the west. The Dallas city limit reaches north across the county line, so about 51,760 residents of the city of Dallas are counted in Collin County. Downtown Dallas is roughly 30 miles south of the McKinney square on US-75.
Cities and towns
Figures are the 2020 census count inside Collin County; Plano, Frisco, Wylie, Richardson, Prosper, Celina and Dallas all cross a county line.
| Place | Type | 2020 population |
|---|---|---|
| Plano (part) | City | 279,929 |
| McKinney | City · county seat | 195,333 |
| Frisco (part) | City | 119,054 |
| Allen | City | 104,648 |
| Wylie (part) | City | 54,644 |
| Dallas (part) | City | 51,760 |
| Richardson (part) | City | 42,264 |
| Prosper (part) | Town | 23,955 |
| Murphy | City | 21,005 |
| Anna | City | 17,073 |
| Princeton | City | 17,065 |
| Celina (part) | City | 15,483 |
| Melissa | City | 13,901 |
| Fairview | Town | 10,372 |
Farmersville, Blue Ridge, Lavon, Lowry Crossing, Lucas, Nevada, Parker, Weston, New Hope and St. Paul round out the incorporated places.
Roads
- US-75 (Central Expressway) – the county's north–south backbone, entering from Richardson and running through Plano, Allen, McKinney, Melissa and Anna toward Sherman.
- Dallas North Tollway – parallel to US-75 about eight miles west, through west Plano, Frisco, Prosper and Celina.
- SH-121 / Sam Rayburn Tollway – the diagonal from the Denton County line at Frisco southeast to US-75 in McKinney.
- SH-190 / President George Bush Turnpike – clips the southern edge through Plano and Richardson, tying US-75 to I-35E and I-30.
- US-380 – the east–west route across the middle of the county through Prosper, McKinney, Princeton and Farmersville.
- SH-5 – the old highway alongside US-75, through Allen, McKinney and Anna.
- SH-78 – southeast from Wylie past Lavon toward Farmersville.
- SH-66, SH-160 and SH-205 – county roads linking Wylie, Blue Ridge and the Rockwall line.
Lavon Lake
Lavon Lake fills the southeastern quarter of the county on the East Fork of the Trinity River, above a U.S. Army Corps of Engineers dam near Wylie. It is the main raw-water source for the North Texas Municipal Water District, which treats it at Wylie and pipes it across Collin, Rockwall and northern Dallas counties — the reason the county could keep adding subdivisions through the 2000s. Water covers about 45 square miles of Collin County, roughly 5 percent of its area, and nearly all of that is Lavon; a sliver of Lake Ray Hubbard reaches the county's southern edge.
Above the lake the county is still farmland. Northeast of McKinney and out toward Blue Ridge and Weston the blackland is planted in wheat, corn and hay, and the towns are a few hundred people apiece. The dividing line is roughly US-380: south of it the county is continuous suburb, north of it the fields start again — but not for much longer, given that Anna, Princeton and Celina each roughly doubled or tripled between 2020 and the 2024 estimates.