Anywhere from nine to 10 million gallons of water per hour flows through the spring, which is the seventh largest spring in the world, and stays at a constant temperature of 58 degrees Fahrenheit.
Hundreds of years ago, Osage Native American Indians hunted, fished and lived around the spring. When Europeans and early settlers came, it was a good place to set up camp and rest up for the next leg of their journey. The first settlers around what is now known as Mammoth Spring, called the spring "Head of the River" because it is the source of the Spring River.
It wasn't until 1857 when Arkansas' first state geologist, Dr. David Dale Owen examined the spring and found out its massive water output that the spring and the town that developed around it became a tourist attraction. Dr. Owen called "the Big Spring" Mammoth Spring in his report because he thought it could be the largest spring in the world. "(He) determined that the source of the Spring River was Mammoth Spring, which was an up swell of water from an extensive system of underground rivers beginning in Missouri," according to the nomination form. The water flows out from the spring about 80 feet below the surface of Spring Lake.
Industry soon emerged with the arrival of the St. Louis and San Francisco (Frisco) Railroad in 1883. In 1887, the Mammoth Spring Improvement Company built the dam, which originally powered the local gristmill.
The dam is a masonry gravity dam. "This masonry gravity dam was built by stacking six limestone slabs on a solid rock base. The widest slab was positioned on the bottom, and each slab was slightly narrower than the one below it, forming a series of small steps. This method of dam construction, devised by French engineer M. De Sazilly in the 1850s, ensured that the hydrostatic force of a body of water would not be enough to overtake the weight of masonry used for the dam," according to the nomination form.
The old town of Mammoth Spring soon grew from a sleepy hollow of 25 people to 950 in 1897. Because of the growing fab of bathing in natural spring waters for their curative powers, Mammoth Spring became a vacationing ground for wealthy individuals from large cities.
In 1957, Mammoth Spring became a state park and developed in about a 20-year period to consisting of 62.5 acres, the dam, a restored 19th century railroad depot and much more.
From about 1925 to 1972, the dam was used by the Arkansas-Missouri Power Company for hydroelectricity.
"Constructed in 1887-88 by the Mammoth Spring Improvement and Water Power Company, the Mammoth Spring Dam powered the Mammoth Spring Roller Mill and Elevator, which ground soft wheat into flour, and the Mammoth Spring Cotton Mill and Cotton Gin," according to the National Register nomination form. "After the Arkansas-Missouri Power Company purchased the Mammoth Spring Dam in 1925, the south turbine well was retrofitted to produce hydropower."
According to the National Register nomination form, it cost the Arkansas-Missouri Power Company $10,670 to purchase the necessary equipment to convert the dam to produce electricity. When in operation, the hydroelectric dam generated about 2,128,875 kilowatt-hours and provided electricity to Mammoth Spring, Ark., Thayer, Koshkonong, Brandsville and West Plains, Mo.
In 1972, the Arkansas-Missouri Power Company donated the dam to the state park because the company decided running the dam was not economically feasible. "The power plant could only operate for 30 minutes out of every hour before it had to shut down and let the lake refill," according to the nomination form.
"The Mammoth Spring Dam retains excellent integrity of location, design, setting, materials, workmanship, feeling and association," says the National Register nomination form. "The dam is still in its original location, and the cut limestone construction of the spillway and turbine wells dates to the dam's construction in 1887-88. The addition of the powerhouse and equipment in 1927 is historic and only adds significance to the Mammoth Spring Dam."
There are several criteria a location has to meet to be placed on the National Register of Historic Places. "The Mammoth Spring Dam and Lake are being nominated to the National Register of Historic Places with statewide significance under Criterion A for their association with the growth and development of Mammoth Spring and Criterion C as a unique intact example of an early stone masonry gravity dam constructed in accordance with M. De Sazilly's model. Futhermore, the Mammoth Spring Dam is far larger than the other National Register-listed 19 century stone masonry gravity dams in the state (Osage Mills Dam, Denton County, BE2993; Ruddell Mill Site, Independence County, IN0274; Spring Mill and Independence County, IN0498) and is the only one later used to generate hydroelectric power for a sizeable population," says the National Register nomination form.
Two other Arkansas locations were also placed on the National Register of Historic Places: The Federal Reserve Bank Building Boundary Increase in Little Rock and the Hartford Commercial District in Hartford.
For more information about the National Register of Historic Places program call the Arkansas Historic Preservation Program at 501-324-9880.