Since as early as 1847 residents of Castroville have conducted a community holiday on or about the 25th of August—the Catholic observance of the Feast of St. Louis. Local tradition recalls that early processions escorted clergy from the priests' house adjacent to St. Louis Church, with clanging of anvils and the blare of the community band.Texas Sesquicentennial 1836-1986
Through the years a picnic became traditional on the church grounds following High Mass. Before the festivities, men smoked sausage and pit-barbecued beef. Women prepared potato salad, cabbage slaw, and desserts. An evening dance in a local establishment ended the day-long celebration.
The St. Louis Society, founded in 1875, traditionally organized the event. Since 1889 the celebration has raised funds for the benefit of the Parish church and school. After the 1920s, the picnic and dance were held at Wernette's Garden. That site (4 blocks NNW) was donated to the parish and renamed Koenig Park in 1949. The dance pavilion there was erected in 1953.
The celebration is now held annually on the Sunday nearest August 25. The procession begins at the church after Mass, and winds through the city to Koenig Park for the picnic lunch and evening dance.