This tank was named after both Robert E. Lee and Ulysses S. Grant

After the tank made its first appearance on the battlefield during WWI, tank design in Europe evolved with faster, better armored, and deadlier tanks. However, U.S. tank design and doctrine development stagnated during the interwar period. When WWII broke out, America's armored corps severely lagged behind Germany's. Seeing the effectiveness of Panzer IIIs and Panzers IVs in France, the U.S. Army ordered a new medium tank with a 75mm gun: the M4 Sherman. In the meantime, the M3 Medium Tank was the best that America had.

America's M2 Light Tank and M2 Medium Tank were fitted with obsolete 37mm guns. To field a tank with a 75mm gun, the M3 Medium Tank was developed in 1940 and fielded in 1941 as a stopgap until the M4 could enter service. However, American tank manufacturers lacked the design experience to fit a 75mm gun in a turret. So, the M3 housed its 75mm gun in an offset sponson on the right side of the hull. This limited the gun's traverse range. To compliment it, a 37mm gun was fitted in a turret.

Britain was keen to order American tanks to reinforce its armored corps in North Africa after abandoning many of its tanks at Dunkirk. However, they were displeased with many aspects of the M3's design including its high profile, hull-mounted gun, the lack of a radio in the turret and inferior armor plating. Addressing some of Britain's concerns, a larger turret was designed with thicker armor and a radio. M3s fitted with the British turret were named "Grant" while M3s with the original U.S. pattern turret were named "Lee." Britain took delivery of both variants and used the names of the Civil War generals to distinguish them.

Of the 6,258 M3s built, 2,887 were sold to the British. 1,685 of them were Grant variants with the British turret design. The M3 first saw action in North Africa in May 1942, surprising the Germans and Italians with the range of its 75mm gun. Five months later, the first M4 Shermans arrived in North Africa and many of Britain's M3s were shipped to India. 777 were supplied to Australia for training and home defense. The M3 was also fielded by the U.S. and the Soviet Union, exclusively in the Lee configuration. Interestingly, the Soviets generally referred to their M3s as Grants.