The Special Committee to whom was referred the petition of the Commercial Base Ball Club praying the privilege of erecting a building at Lafayette Park reported the same back and recommended that it be referred to the Board of Improvements of Lafayette Park. Report adopted.-Missouri Republican, June 27, 1863
Not only was the Commercial Club active during the war but they were in a position to attempt to make improvements to their grounds at Lafayette Park. I think this speaks to the possibility that not only was a great deal of baseball being played in St. Louis during the Civil War but it was thriving and growing to the point were the Commercials wanted to build a permanent clubhouse on their grounds. Also, the environment in St. Louis was such that this was possible.
I think it's interesting to compare this petition to the Common Council to the ones in 1861, when both the Cyclones and Commercials were presenting petitions for the use of Lafayette Park as a baseball ground and for permission to improve the grounds. That was just before the war broke out. Here we see pretty much the exact same process taking place at the height of the war. This report was adopted a few days before Gettysburg and the fall of Vicksburg. So, at a moment when the war was raging and still in doubt, the Commercials were looking to make improvements to the grounds at Lafayette Park.
Also, it should be noted that I thought Lafayette Park was not being used for baseball during the war. The secondary sources stated that the park was seized by the military and used as an encampment for troops. Now that did happen and the Union army was using the park by the summer of 1861. But it also appears that the Commercials were also using the park in 1862 and 1863. If you're looking for evidence that soldiers, unfamiliar with the Regulation game, was exposed to baseball during the war, here's a place you should look. It seems very possible that both the army and the Commercials were using Lafayette Park at the same time. If that's true, the Commercials must have been getting great crowds for their games, as I'm sure the soldiers, bored with camp life, were looking for any form of entertainment and wandered over to see some baseball. While I'm still not particularly convinced that the war helped to spread the game (and by not particularly convinced, I mean not convinced at all), I can see the possibility here to gather evidence in support of that argument.