No dispute about that, by summer of 1861 both sides had begun to raise up fearsome armies of huge numbers.
But in January or April 1861 it was a very different picture indeed.
The entire United States Army then was about 17,000 strong, over half scattered in forts out west, some in Texas under command of a promising colonel named Robert E. Lee.
This count of 17,000 did not change until after Fort Sumter (April 12) when Lincoln called up another 75,000 from the states (some of whom refused).
In the mean time, on March 3 the Confederate Congress called for 100,000 troops and then on May 9 (after formally declaring war against the USA) authorized another 400,000 making the Confederate Army 500,000 in total.
Yes, of course, in the long run the Union Army vastly outnumbered Confederates, but that was far from the case at war's beginning, and took many months of buildup.
Two keywords from the above statement: "called for" and "authorized".
BTW, when you cut and paste from another website you should have the common courtesy to post a link to the site that you're plagiarizing from.