Meramec Caverns is the collective name for a 4.6 miles (7.4 km) cavern system in the Ozarks

The Ozarks

The Ozarks are a physiographic and geologic highland region of the central United States. It covers much of the southern half of Missouri and an extensive portion of northwestern and north central Arkansas...

, near Stanton

Stanton, Missouri

Stanton is an unincorporated community in Franklin County, Missouri, United States. It lies on Interstate 44 at the junction with Missouri Supplemental Route W. Prior to Interstate 44, it was an important town on U.S. Route 66 due to the nearby Meramec Caverns very prominently advertised up and...

, Missouri

Missouri

Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...

. The caverns were formed from the erosion of large limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 deposits over millions of years. Pre-Columbian

Pre-Columbian

The pre-Columbian era incorporates all period subdivisions in the history and prehistory of the Americas before the appearance of significant European influences on the American continents, spanning the time of the original settlement in the Upper Paleolithic period to European colonization during...

 Native American

Native Americans in the United States

Native Americans in the United States are the indigenous peoples in North America within the boundaries of the present-day continental United States, parts of Alaska, and the island state of Hawaii. They are composed of numerous, distinct tribes, states, and ethnic groups, many of which survive as...

 artifacts have been found in the caverns. Currently the cavern system is a tourist attraction

Tourist attraction

A tourist attraction is a place of interest where tourists visit, typically for its inherent or exhibited cultural value, historical significance, natural or built beauty, or amusement opportunities....

, with more than fifty billboards along Interstate 44

Interstate 44

Interstate 44 is a major highway in the central United States. Its western terminus is in Wichita Falls, Texas at a concurrency with US 277, US 281 and US 287; its eastern terminus is at the Illinois state line on the Poplar Street Bridge over the Mississippi River in St...

 and is considered one of the primary attractions along former U.S. Highway 66. Meramec Caverns is the most-visited cave in Missouri with some 150,000 visitors annually. Meramec Caverns is ranked #171 on CaverBob.com's USA Long Cave list.

History

The Meramac Caverns have existed for the past 400 million years, slowly forming through deposits of limestone. Centuries ago, Native Americans used the cavern system for shelter. The first cave west of the Mississippi River to be explored by Europeans, it was "discovered" in 1722 by a French miner. During the 18th century, the cave was used for extracting saltpeter

Potassium nitrate

Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...

 for the manufacture of gunpowder

Gunpowder

Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...

. In the Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

 era, the Union Army

Union Army

The Union Army was the land force that fought for the Union during the American Civil War. It was also known as the Federal Army, the U.S. Army, the Northern Army and the National Army...

 used the caves as a saltpeter plant, but the plant was discovered and destroyed by Confederate guerrillas, including future famous outlaw Jesse James. Reportedly, James and his brother and partner in crime Frank used the caves as a hideout in the 1870s. One legend claims that the sheriff

Sheriff

A sheriff is in principle a legal official with responsibility for a county. In practice, the specific combination of legal, political, and ceremonial duties of a sheriff varies greatly from country to country....

 sat in front of the cave, waiting for Jesse and his gang to emerge; however, they had found another exit. In 1933, the extended cave system was discovered, revealing the present 4.6 miles (7.4 km), and was introduced to the public as a tourist attraction in 1935 by Lester B. Dill, who invented the bumper sticker

Bumper sticker

A bumper sticker is an adhesive label or sticker with a message, intended to be attached to the bumper of an automobile and to be read by the occupants of other vehicles - although they are often stuck onto other objects...

 as a means of promoting the caverns.

In 1960, Meramec Caverns began to rent billboard

Billboard

Billboard is a weekly American magazine devoted to the music industry, and is one of the oldest trade magazines in the world. It maintains several internationally recognized music charts that track the most popular songs and albums in various categories on a weekly basis...

space in the caverns. The owners claimed this was the only underground billboard in the world.