It is expected that the new grounds, negotiations for which are proceeding, will be inaugurated with a game with the Chicago Club, after which the St. Louis Club will set out on its first Eastern tour. The new grounds will, it is said, be very near the city (a desideratum the present grounds lack), and very ample both for the players and spectators.
-Chicago Tribune, November 22, 1874
Sometime in early November of 1874, the men organizing the Brown Stockings held a meeting and were selling subscriptions to stock in the St. Louis Base Ball Club. One of the men at the meeting who subscribed was Thomas McNeary, owner of the Compton Avenue grounds and operator of the Red Stockings Base Ball Club. This, I believe, is a significant piece of information because it speaks to McNeary's state of mind with regards to his plans for 1875. If McNeary had been planning, in November of 1874, to enter the Reds in the National Association, I don't believe that he would have been involved in helping to organize the Brown Stockings, a club that would have been competing against his club. It doesn't make sense unless McNeary did not plan on having the Reds join the NA.
So what was McNeary doing? I believe that his goal was to have the new Brown Stockings play at the Compton Avenue grounds. If he could achieve that , he would arguably have the two best clubs in the city playing at his park - the professional Browns and the amateur Reds. It is clear from the article in the Tribune, quoted above, that the Browns had not made any firm plans about their home grounds by late November 1874. Therefore, it is my contention that the idea to enter the Reds in the NA dates to sometime after late November 1874.
The information I posted yesterday shows that by the end of January 1875, that decision had essentially been made or that, at the very least, McNeary had come to the conclusion that the Browns wouldn't be playing at the Compton Avenue grounds and was making other plans. So I date the decision to enter the Reds in the NA to December 1874 or January 1875 and the reason that McNeary made the decision was because the Browns rejected his offer to have the club play at his baseball grounds.