Early pioneers settled along the Trinity River and its tributaries and on the edge of the frontier as it moved westward.

Settlers were scarce, however, until the Republic of Texas approved an impresario grant in 1841 with the Texas Emigration and Land Company based in Louisville, Kentucky. W.S. Peters led the group of twenty investors, and the grant became known as the Peters Colony. The contracts eventually covered all of Northeast Texas. The colony's land office was established near Hebron in the southeast corner of present-day Denton County.

After Texas joined the union, promises of U.S. Army protection from marauding Indians prompted a new wave of immigration.

The new county, carved out of Fannin County, was named for John B. Denton, a pioneer preacher and lawyer who had been killed in an Indian fight in 1841.

The pioneers chose a county seat along Pecan Creek and named it Pinckneyville.  Pinckneyville lasted only two years. Water shortages forced the fledgling community to move, first in February 1848 to a new site they named Alton a few miles south and again in late 1848 to another site near Hickory Creek. The Hickory Creek location also was named Old Alton and it remained the seat of Denton County government for about ten years.

By 1856, the little settlement of Old Alton was thriving. Old Alton boasted several homes, a blacksmith shop, three stores, a saloon, hotel and bar, two doctors, several lawyers, and a cemetery, and was headquarters for the Denton County Land District.

By 1857, however, Denton County was ready to move the county seat again. County residents wanted a county seat more central to the settlements in Pilot Point in the north and Lewisville in the south. Old Alton residents voted to move again. This time they called the new county seat Denton. Lots for the original Township of Denton were auctioned on January 10, 1857.

The first courthouse in Denton was a two-story frame structure on the north side of the downtown square. The building burned in 1875, destroying most of the county records. A brick courthouse was then built in the center of the square, a two-story building with a tall central tower. Lightning damaged that building and it was condemned and demolished in 1894. Construction of the present Courthouse-on-the-Square began in 1895. The cornerstone was laid in 1896, and the courthouse was dedicated in 1897.

For a decade, Denton County was on the northeast Texas frontier. Cattle and horses ranged on the unfenced prairies. Residents were engaged in ranching and subsistence farming. John S. Chisum, who became the most famous cattleman in the West, operated his first ranch in Denton County.

In 1860, Denton County population was 4,780. In the 1870s, population grew to 18,143. Subsistence farming gave way to cotton farming in the blackland and wheat farming on the prairies. Railroads came through to boost the economy more.

1900's

From 1890 to 1920, Denton County ranked either first or second in wheat production in Texas.

Denton County covers 911 square miles in north central Texas. The Eastern Cross Timbers juts through the central part of the county. Blackland prairie covers its western half and a slice along its eastern edge.

Denton county population grew from 47,432 in 1960 to 143,126 in 1980.

Many new rural residents owned small spreads. The horse farms began replacing cattle ranches in the 1970s.  Large horse ranches were scattered through the county; in 1983 horses brought in $17,207,400, a significantly larger income than that from any other agricultural product.

Newcomers and many older residents returned much of Denton County's rich cropland to pasture.

2000's

By the year 2000, the northern area of the county was a center for horse ranches and a balanced farming region producing wheat, cotton, beef and dairy cattle.