The title described the Mission San Antonio de Valero in San Antonio, Texas that was built in the 17th century to convert the native Americans to Christianity. By 1800 the mission had been abandoned and was used as a garrison before the Texas soldiers occupied the building prior to the historic battle in 1836 which resulted in the cry of "Remember the Alamo!"
This episode takes place in the Alamo Mission, San Antonio, Texas on March 6, 1836 and in Arizona in 1968.
Stock footage from The Alamo (1960) pads out the run time. Laurence Harvey as William Travis and Richard Widmark as James Bowie can be seen in long distance shots.