Complex sentence: Texas herds were taken up the Shawnee Trail as early as the 1840s, and use of the route gradually increased, but, by 1853, trouble had begun to plague some of the drovers.
Split into simpler sentences: Texas herds were taken up the Shawnee Trail as early as the 1840s, and use of the route gradually increased. But by 1853 trouble had begun to plague some of the drovers.