Before colonization, this valley was a lush thicket of woodlands and brush nourished by rich soil deposited by the Rio Grande, and across the Lower Valley it supported a broad variety of plants and animals, with species more common north of the river coexisting with those more common to the south. In the 18th century, land grants were made to the original Spanish settlers of the Rio Grande Valley in narrow river-access divisions called porciones, and the grant here was part of Porción 50, awarded to Jose Antonio Zamora by the Ancient Jurisdiction of Reynosa, Mexico. At the beginning of the 20th century, developers and farmers began large-scale clearing of the land, and by the 1930s much of the Rio Grande Valley had been cleared for citrus groves. In 1944, more than 586 acres of native landscape here were saved and donated to the Texas State Parks Board by Lloyd M. and Edna Ruth (Dolly) Bentsen, and Elmer C. and Marie J. Bentsen. Cedar elm, hackberry, and mesquite mix with ebony, Mexican ash, and anaqua trees, and along with the brushlands they provide habitat for countless mammals, reptiles, and resident and migrant birds. The park preserves part of the valley's ancient environment for education and enjoyment.