Manuel Castro was a King Ranch semi-pro baseball player and umpire. The team called the King Ranch Cowboys began as a semi-pro team of ranch employees in the 1940s. They were better than most teams in South Texas and became known in the region. Castro collected baseball publications in the 1960s and 1970s which his niece, Cynthia S. Castro donated to the John E. Conner Museum in November 1999. The museum transferred the documents to the South Texas Archives in 2000.