Santa Ana National Wildlife Refuge is a 2,080-acre natural preserve on the banks of the Rio Grande seven miles south of Alamo in Hidalgo County. The refuge is noted for its unusual birds, mammals, butterflies, and plants. The site was acquired in 1943 by the federal government to protect a remnant of the subtropical Rio Grande Delta riparian forest, most of which had been lost to agricultural clearing. The refuge lies in El Agostadero del Gato (the Pasture of the Cat), Los Toritos (the Little Bulls), and Santa Ana land grants, but is largely within the latter. The Santa Ana grant was conveyed by the Mexican state of Tamaulipas, in which it then lay, to Benigno Leal on May 19, 1834. A ranch house of handmade bricks was built in the Rancho de Adentro (Inside Ranch), and a cemetery was established near the ranch buildings. No trace of the ranch house remains, but Santa Ana Cemetery is still visible, partly enclosed by the original hand carved Texas ebony fence which protects approximately thirty graves and a tomb built of hand formed bricks. The tomb originally contained the remains of Cristoval Leal, adopted son of the original grantee, and his wife María Rafaela Treviño. During the border bandit raids of 1915–16, the tomb was broken into. It remained open, exposing scattered bones, until 1943. After the federal government purchased the ranch, the tomb was repaired. Today the cemetery is protected and maintained and is one of the main attractions in the refuge.
As a remnant subtropical forest surrounded by cleared agricultural land and approached by urban sprawl, the refuge protects some of the few ocelots and jaguarundis remaining wild in the United States. Valid sightings of these elusive cats have been documented, and refuge biologists hope that their numbers will increase and spread to other sanctuaries along the Lower Rio Grande. In addition to these rare cats, over 33 species of other mammals, 372 species of birds, 200 species of butterflies, and 34 species of reptiles have been recorded in Santa Ana. Especially noteworthy birds are chachalaca, green jay, and alta mira oriole. Santa Ana has over 450 plant species. It is the northernmost range of many tropical plants and also has many species from the temperate zone. Although the land surface elevation varies only a few feet, five different mini habitats correspond to the slight elevation differences, soil types, and nearness to water in refuge lakes or in the Rio Grande. Resacas display retama (Parkinsonia aculeata), rattlebox (Sesbania drummondii) and black mimosa (Mimosa nigra). Upland Thorn Forest displays cenizo (Leucophyllum frutescens), Texas ebony (Pithecellobium ebano), guayacan (Guaiacum angustifolia), trecul yucca (Yucca treculeana), coma (Condalia hookerii), and nine species of cacti. Bottomland Forest displays cedar elm (Ulmus crassifolia), tepeguaje (Leucaena pulverulenta), and Rio Grande ash (Fraxinus berlandierana). Riparian Terraces display black willow (Salix nigra) and butterfly bush (Buddleja sessiliflora). Mudflats display few plants. The rarest plants in Santa Ana include Esenbeckia runyonii, which was thought to be extinct in the wild until rediscovered in 1986, and Santa Ana capparis (Capparis incana). In 1967 the refuge was designated a Registered Natural Landmark "because of its exceptional value in illustrating the natural history of the United States of America." It was one of the first federal areas placed in this category.
A sixty-eight-acre Texas Ebony Natural Area, located near the Rio Grande and east of the Jaguarundi Trail, has been set aside for research and educational purposes. Santa Ana Refuge has a visitor center that houses administrative offices, a museum, and an auditorium. Twelve miles of foot trails wind through the reserve, and a tour tram travels a seven-mile route during winter months. Although the primary purpose of the refuge is the protection of wild animals and the preservation of their habitat, the staff is dedicated to increasing public awareness of the critical need to conserve wildlife, plant species, and river systems. Visitors are invited to see interpretive films in the auditorium and to walk the trails. Santa Ana is an island of natural greenery surrounded by intensive farming and urban development. Visitors increased from 133,220 in 1983 to 273,990 in 1988.