The M59 was designed by FMC to replace the M75. It featured the standard box-like hull and layout of US APCs, with the driver at the left front and the commander to his right, behind which lies the troop compartment that could carry 10 fully loaded infantrymen. These could be unloaded through a hydraulically-operated rear ramp although a roof hatch was also provided as was a door in the ramp in case it jammed. Armament was the typical 12.7-mm M2 Browning installed in a number of different cupolas. In order to reduce costs, two civilian GM engines were installed but these proved to be underpowered in practice. Another disadvantage was the reduced armor protection compared to the M75, although it had the benefit of being fully amphibious. The production run of the M59 was considerably higher than that of the more expensive M75, but reliability issues resulted in its replacement by the M113 after just over a decade of US service, during which it saw action early in the Vietnam War. Foreign operators included Brazil, Ethiopia, Greece, Lebanon, Turkey and South Vietnam.

The T59 was developed in the early 1950s and featured twin Cadillac engines that were eventually replaced with GM engines in the T59E1, which was eventually re-designated M56. The only other major variant was the M84 107-mm mortar carrier, but the base version was also used as an ambulance, load carrier, command vehicle and weapons carrier.