In 1874, according to E.H. Tobias, the Chicago White Stockings "came to St. Louis under an arrangement to play four games each with the Empire, Red Stocking and Turner Clubs..." These were probably the three best clubs in St. Louis at the time and the Chicagos cleaned their clocks. While there were a couple of close games, the White Stockings went undefeated on their St. Louis trip and embarrassed the St. Louis baseball fraternity.
Below is the dates of the games played and their results:
April 21 Chicago 24 Empire 2
April 23 Chicago 6 Reds 0
April 26 Chicago 6 Empire 4
April 28 Chicago 22 Turners 5
April 29 Chicago 30 Empire 9
April 30 Chicago 31 Reds 10
May 1 Chicago 21 Empire 10
May 2 Chicago 31 Reds 13
Thankfully, the weather in St. Louis was rather rainy (as it usually is at that time of year) and the rest of the games were unable to be played-although the Reds did make a trip to Chicago and finished their series with the White Stockings on May 6 (when they promptly lost by a score of 14-7). The Chicagos came to St. Louis, went 7-0 on the trip and outscored the best teams in St. Louis by an aggregate score of 171-53. If you count the Reds game in Chicago, the White Stockings were 8-0 against the best St. Louis had to offer and had a run differential of +125.
To add insult to injury, the Chicagos "perpetrated highway robbery while (in St. Louis) and secretly carried their spoils home with them in the person of Johnnie Peters, second base of the Red Stockings, and (Dan) Collins, the Empire pitcher." So not only did the White Stockings come in and crush everybody, they also stole two of the best players in town.
You can date the beginning of the movement to create a professional baseball team in St. Louis...It was this crushing performance by the Chicagos and the humiliation suffered by the St. Louis baseball community that set into motion the events that would lead to the creation of the Brown Stockings. It also puts into perspective the celebration that erupted following the Brown Stockings 10-0 victory over the White Stockings on May 6, 1875. The Browns 4-3 win over the Chicagos two days later was just icing on the cake (and payback for stealing Peters and Collins).
Edit: This little story keeps getting worse. It seems that the White Stockings came back to St. Louis in October of 1874 and continued their dominance over the St. Louis clubs. On October 15, they defeated the Reds 17-3 and two days later they beat the Empires 13-0, the first time in the proud history of the Empire Base Ball Club that the team had ever been shutout. So for those scoring at home, the Chicagos were 11-0 against St. Louis clubs in 1874, outscoring them 215-63 for a run differential of +152.
Tired of getting beaten on the diamond and unable to accept the idea of losing to Chicago in anything, the St. Louis baseball fraternity, led by former members of the old Union Club, put together the first openly professional baseball team in the history of St. Louis and brought in the finest Eastern talent they could sign. While there is no doubt that St. Louis would have had professional, major league baseball eventually, the unmitigated beating that the Chicagos put on the best "amateur" clubs in St. Louis forced the St. Louis baseball fraternity into action. After the Chicago professionals roared through St. Louis in 1874 and humiliated the pride of St. Louis baseball, things changed.