Hagerman Fossil Beds National Monument ⓘ

During the Pliocene, this region’s lush wetlands, forests, and grasslands teemed with life. By the time humans began to make a home here, the Hagerman Valley had become arid sagebrush scrub, and many of the strange and fascinating fossil creatures we study today had long been extinct.

People have lived here for thousands of years. Since time immemorial, Shoshonean peoples have camped along the Snake River ( Bia Ogwaide ), fishing its waters for salmon, steelhead, and sturgeon. It is likely that they were the first to see fossils eroding out of the steep bluffs along the river. By the mid-1800s, life was turned upside-down for the Shoshoneans. The Oregon Trail brought thousands of newcomers from the eastern United States, all in search of new land and opportunity out West. On an arduous 2,000-mile journey, wagon trains found respite in the Hagerman Valley, where the river finally emerged from its deep, inaccessible canyon, and fresh springs bubbled out of the rock. The Shoshoneans were welcoming, trading fish and other resources with the weary emigrants. But resources were soon strained, and as newcomers began to settle in the region, conflict arose. By 1868, Shoshonean peoples were removed from their ancestral lands and placed on reservations. Though the Shoshoneans were forced to endure great hardship, today they are, in their own words, “recovering and thriving.” This landscape remains integral to their culture and identity. Learn more about the Shoshone-Bannock Tribes' relationship with Hagerman Fossil Beds National Monument today. Some of the first non-indigenous settlers in this region were ranchers and miners. In the 1870s, gold mining brought enormous numbers of Chinese immigrants to Idaho. Making up nearly a third of the territory’s population in the 1870s, the Hagerman Valley had its own community of Chinese immigrant miners. Within a short time, exclusionary laws and dried-up opportunities ended this period of Idaho’s history. By the early 1900s, improvements to irrigation allowed a small but vibrant agricultural community to thrive in the Hagerman Valley. The town was named after Stanley Hageman, who helped to establish the first post office (a misspelling of his name somehow stuck.) Dams, roads, and other infrastructure were added over time, but Hagerman remains a quiet farming community to this day.

In 1928, a Hagerman rancher named Elmer Cook made a peculiar discovery: fossils were eroding out of the rock along the Snake River. Although Elmer was likely not the first to stumble across fossils, he was the first to recognize that they might be significant. Elmer showed the fossils to Dr. H.T. Stearns of the United States Geological Survey, who in turn contacted Dr. J.W. Gidley of the Smithsonian Institution in Washington, D.C. The following summer, Gidley brought the first of four fossil expeditions to Hagerman. In 1929, 1930, 1931, and 1934, the expedition blasted open the steep bluffs along the river, scraping away sediment with teams of horses. Digging as deep as 60 feet, the expedition unearthed the remains of over 200 Pliocene horses. The Hagerman Horse Quarry remains the largest single find of Equus simplicidens , a predecessor of modern horses that lived 4 to 3 million years ago. The exceptional find included over 20 complete skeletons and individuals of all life stages and sexes, providing researchers with a rare look at an entire population. In addition to the Hagerman Horse, the expedition identified dozens of other species, including completely new species like the peccary Platygonus pearcei . In 1929 alone, three tons of fossils were shipped from Hagerman back to the Smithsonian in Washington, D.C. Elmer Cook remained heavily involved in the excavations. A lifelong citizen scientist, he maintained a personal fossil collection, and he is credited for several specimens in the Smithsonian’s collection.

The Smithsonian expeditions focused primarily on large and exciting new finds, such as horses, ground sloths, mastodons, and saber-toothed cats. A few decades later, paleontologists returned to Hagerman to take a closer look. The new generation of researchers combed the site for the smaller fossils and fragments of fossils the earlier excavations had overlooked, such as rodents, fish, frogs, and turtles. These finds have offered valuable clues about the ecology and climate of Pliocene Hagerman. In 1988, Congress established Hagerman Fossil Beds National Monument. Part of the same legislation that created nearby City of Rocks National Reserve and other public lands across the country, the Arizona-Idaho Conservation Act set aside 4,394 acres in the Hagerman Valley for paleontological research.

Scientific research continues at Hagerman. Surface collecting of fossils is occasionally done, but there are currently no active excavations. A new research lab was completed in 2021, creating a new home for Hagerman’s fossil collection and helping to facilitate research at the site. In 2021, Hagerman Fossil Beds entered a 25-year partnership with Idaho Department of Parks and Recreation, which manages the six units of Thousand Springs State Park. The new Thousand Springs Visitor Center at the Billingsley Creek unit, opening in 2022, will feature all-new fossil exhibits and host ranger programs and other activities. Hagerman Fossil Beds remains one of the world’s richest Pliocene fossil sites. To date, tens of thousands of fossils have been collected here, many of which are now in the collection of the Smithsonian and other museums across the country. These fossils belong to over 140 identified species, several of which are type specimens, new to science when they were uncovered. Hagerman is also considered one of the world’s key sites for the study of horse evolution, and the discoveries made here have shaped our understanding of this familiar animal.

Much has changed in Idaho since the Pliocene, when the Hagerman horse, ancient camels, and mastodons, thrived in forests and on grasslands. Over 20 inches of precipitation a year created a lush environment for the development and survival of a wide variety of animals. Learn more about Hagerman's ancient past. Today, the Hagerman area receives less than 10 inches of precipitation. However, due to the Snake River, natural springs, and other water sources, the area is still able to support an incredible diverse species population. The riparian zones of the Hagerman area support habitat that is important for migratory waterfowl and other many other species.

The predominant naturally-occurring vegetation on the Monument is composed of the sagebrush steppe plant communities once common to much of the intermountain region of southern Idaho. These shrub steppe communities include a dominant shrub, often sagebrush, interspersed with open, sparsely vegetated areas of grasses and forbs. The steep slopes of the Monument’s bluffs west of the Snake River provide an environment that contributes to the diversity of plant species. In addition, a riparian zone and localized wetlands occur along the Reservoir.

The monument is home to a variety of native grasses such as: wheatgrass, bluegrass, Indian ricegrass, and Great Basin wildrye. Flora on the upland plateau was once a vast complex of Wyoming big sagebrush ( Artemisia tridentata ver. wyomingensis ) association. Greasewood ( Sarcobatus vermiculatus ) and rabbitbrush are the dominant shrubs where the soils are more alkaline. Scattered occurrences of four-wing saltbush ( Atriplex species ) occur where soils contain more calcite. Riparian vegetation includes black cottonwood ( Populus trichocarpa ), bulrush ( Scirpus spp .), and cattails ( Typha spp .). Willows ( Salix spp .) are most common in the vicinity of the dam and the falls to the north and south of the Monument.

Common mammal species include mule deer, red foxes, coyotes, badgers, cottontail rabbits, and yellow-bellied marmots. River otter, beaver, muskrat, mink, and other furbearers are found in and around Hagerman’s ponds, marshes, and waterways. A variety of wading and shorebirds nest at Hagerman, while others stop briefly before continuing their northward migration. The short-eared owl and the western screech owl commonly nest in Hagerman. The ring-necked pheasant, grey partridge, and California quail also call Hagerman home. Black-crowned night herons, great blue herons, Virginia rails, American avocets, and spotted sandpipers are some of the species that stop briefly. Ospreys, bald eagles, peregrine falcons, and rough-legged hawks are seasonal guests. Marsh wrens, rufous-sided towhees, and numerous warblers species find sanctuary within the riparian areas, while horned larks, vesper sparrows, and northern orioles feed and nest among upland and wooded habitats. Striped whip snakes, western rattlesnakes, and gopher snakes hunt among rock-strewn boulder fields, while short-horned, western whiptail and sagebrush lizards bask in the sun. Western and Great Basin spadefoot toads inhabit the various moist areas and bullfrogs, northern leopard frogs, pacific tree frogs, and striped chorus frogs can be heard singing in the distance.

Species of fish in this stretch of the Snake River include rainbow trout ( Salmo gairdneri ), small-mouth bass ( Micropterus dolomieui ), chub ( Couesius plumbeus ), suckers ( Catostomus spp .), and non-native carp ( Cyprinus carpio ). Sturgeon ( Acipenser transmontanus ), although once plentiful, are now rare.

Much of the Snake River and many of its reaches have been declared as critical habitat for the Snake River sockeye salmon ( Oncorhynchus nerka ), a federally listed endangered species, and the Snake River fall Chinook salmon ( Oncorhynchus tschawytscha ), a federally listed threatened species. In addition, the entire Snake River Basin has been designated as an Evolutionary Significant Unit for the West Coast steelhead ( Oncorhynchus mykiss ).

Livestock grazing prior to establishment of the Monument in 1988 also undoubtedly contributed to alteration of soils, loss of native grasses, and establishment of non-native plant species. Non-native plant species known to be present include Russian olive ( Eleagnus angustifolia ), Russian thistle ( Salsola kali ), quackgrass ( Agropyron repens ), cheat grass ( Bromus tectorum ), blue mustard ( Chorispora tenella ), tansymustard ( Descurainia sophia ), tumble-mustard ( Sisymbrium altissimum ), and medusa head (Taeniatherum caput-medusae ). These and other non-native species likely to be present, compete with the Monument's native plant communities, disrupting ecosystem processes.