The 1866 Yellowboy lever-action rifle was a marked improvement over the Henry rifle. It was the first true cowboy lever-action rifle, and the first rifle widely carried in a cowboy-style saddle scabbard.
The Yellowboy had a convenient new type of loading gate, devised by Winchester plant superintendent Nelson King. The gate passed cartridges through the side of the receiver. This improvement made the lever action more functional and allowed for the installation of a wooden fore-end.
The handy carbine version of the 1866 Yellowboy was a hit worldwide. Chief Sitting Bull had one; the forces of Benito Juarez used the rifles in Mexico; and the Turkish Army used the new Winchester Yellowboy against the Russians.