The area’s population grew slowly at first. Settlers found that the native grasses would only feed grazing animals well when it was green, and the soil, though fertile, was a quagmire when it rained, so transportation of agricultural goods was nearly impossible. Enter the Houston and Texas Central Railroad in 1872. With reliable transportation, people and goods could move in and out of McKinney, and this development stimulated a time of unprecedented growth in the town.

Over the next 50 years, cotton became a major source of revenue in Collin County. In 1860, the yield was 16 bales, and in 1870 it was 4,371 bales. In 1870, there was one cotton gin in McKinney, but by 1876, there were four. A cotton compress began operation in 1892 and was still in operation until the mid-1980s. The first textile mill – The Texas Cotton Mill Company – was opened in McKinney in 1910. It was one of only two mills west of the Mississippi that manufactured color-print cloth. It later became a major manufacturer of denim.