After the Civil War, there were cattle everywhere. The north wanted the beef, so southerners started up cattle drives. Cattle drives were where cowboys herded up a ton of cattle and leaded them north to be butchered.
After the Civil War, the north had a demand for beef. Southerners found this as a way to get rich, so they created cattle drives to get the cattle to the factories in the north to be butchered for meat and other products.