10
There are 40 Generals Currently on Active Duty. This does not count the Generals that are in the National Guard and Reserve who have been activated or otherwise. http://en.wikipedia.org/wiki/List_of_active_duty_United_States_four-star_officers
Many
1 full general, 5 lieutenant generals and about 60 major generals
5
4 star generals are in the US
300
two hundred and fifty six
3
none
There is no information on how many commanding generals President Lincoln had gone through by June 1863. General George Meade commanded the Union army and General Robert E. Lee commanded the Confederate army.
During World War II, there were a total of five four-star generals who commanded the US Army. These generals were George Marshall, Douglas MacArthur, Dwight D. Eisenhower, Henry "Hap" Arnold, and Omar Bradley. Each of these generals played a crucial role in leading the US Army to victory in various theaters of the war.
As the US Civil War unfolded, the US army was small and did not have many generals. In order to command all the Union recruits, new generals had to be appointed. In 1861, Lincoln appointed one hundred and twenty six generals.