Rangerville Park is on Rangerville Road, which took its name from the Texas Rangers' camp that was located near Rangerville Road and Old Military Highway back in the early 1900s. In fact, when Harlingen was just a township, it was known as "Six-Shooter Junction" because most of the first Anglos to live here were Texas Rangers and Border Patrol.
Today this 24 acre park holds two pavilions, 3 athletic fields, covered picnic shelters, and a newly remodeled playground with some handicap swings. It is the site of Harlingen's Halloween in the Park and has a 3/4 mile trail that circles the park.
Finding this cache should be a fairly easy park and grab, if you are clever.