Because that's where the railhead was.
Kansas had railroads
It was a trail used to move cattle from Texas, where Chisolm started, north to Kansas where they have either passed through to further north or sold to cattle buyers in that state.
The herding of cattle from Texas to railroad centers to the north was called a cattle drive. Cattle drives took many months to complete. Some of the cowboys would drive the cattle to Kansas and not want to go back to the ranch after being paid. Then ranchers would have to hire more hands the next cattle drive season.
The area from Kansas to Montana was referred to as the cattle kingdom because this was an area where the cattle outnumbered humans. Kansas and Montana were, and still are, high beef production states.
cattle drive
The took them to a stockyard like Kansas City where they put them in cattle cars.
Sidney, Ogallala and North Platte by 1868.
Nebraska is obviously due north of Kansas
Before the arrival of the railways, cattle were driven to market, known as a cattle drive. When the railways arrived, the cattle were driven to the nearest railhead.
to go up north
Cattle.
Abilene, Kansas