1800s One of the first examples of bicycles modified specifically for off-road use is the expedition of Buffalo Soldiers from Missoula, Montana to Yellowstone in August 1896.  The Swiss military had its first bike regiment in 1891.  1900s–1960s Bicycles were ridden off-road by road racing cyclists who used cyclo-cross as a means of keeping fit during the winter. Cyclo-cross eventually became a sport in its own right in the 1940s, with the first world championship taking place in 1950. Between 1951 and 1956, the French Velo Cross Club Parisien (VCCP), comprising about twenty-one young cyclists from the outskirts of Paris where they were born, developed a sport that was remarkably akin to present-day mountain biking. The Rough Stuff Fellowship was established in 1955 by off-road cyclists in the United Kingdom. In Oregon, one Chemeketan club member, D. Gwynn, built a rough terrain trail bicycle in 1966. He named it a "mountain bicycle" for its intended place of use. This may be the first use of that name. In England in 1968, Geoff Apps, a motorbike trials rider, began experimenting with off-road bicycle designs. By 1979 he had developed a custom built lightweight bicycle which was uniquely suited to the wet and muddy off-road conditions found in the south-east of England. They were designed around 2 inch x 650b Nokian snow tyres though a 700x47c (28 in.) version was also produced. These were sold under the Cleland Cycles brand until late 1984. Bikes based on the Cleland design were also sold by English Cycles and Highpath Engineering until the early 1990s.
1970s–1980s There were several groups of riders in different areas of the U.S.A. who can make valid claims to playing a part in the birth of the sport. Riders in Crested Butte, Colorado and Cupertino, California tinkered with bikes and adapted them to the rigors of off-road riding. Modified heavy cruiser bicycles, old 1930s and '40s Schwinn bicycles retrofitted with better brakes and fat tires, were used for freewheeling down mountain trails in Marin County, California in the mid-to-late 1970s. At the time, there were no mountain bikes. The earliest ancestors of modern mountain bikes were based around frames from cruiser bicycles such as those made by Schwinn. The Schwinn Excelsior was the frame of choice due to its geometry. Riders used balloon-tired cruisers and modified them with gears and motocross or BMX-style handlebars, creating "klunkers". The term would also be used as a verb since the term "mountain biking" was not yet in use. Riders would race down mountain fireroads, causing the hub brake to burn the grease inside, requiring the riders to repack the bearings. These were called "Repack Races" and triggered the first innovations in mountain bike technology as well as the initial interest of the public (on Mt. Tamalpais in Marin CA, there is still a trail titled "Repack"- in reference to these early competitions). The sport originated in California on Marin County's Mount Tamalpais.
It was not until the late 1970s and early 1980s that road bicycle companies started to manufacture mountain bicycles using high-tech lightweight materials. Joe Breeze is normally credited with introducing the first purpose-built mountain bike in 1978. Tom Ritchey then went on to make frames for a company called MountainBikes, a partnership between Gary Fisher, Charlie Kelly and Tom Ritchey. Tom Ritchey, a welder with skills in frame building, also built the original bikes. The company's three partners eventually dissolved their partnership, and the company became Fisher Mountain Bikes, while Tom Ritchey started his own frame shop. The first mountain bikes were basically road bicycle frames (with heavier tubing and different geometry) with a wider frame and fork to allow for a wider tire. The handlebars were also different in that they were a straight, transverse-mounted handlebar, rather than the dropped, curved handlebars that are typically installed on road racing bicycles. Also, some of the parts on early production mountain bicycles were taken from the BMX bicycle. Other contributors were Otis Guy and Keith Bontrager.
Tom Ritchey built the first regularly available mountain bike frame, which was accessorized by Gary Fisher and Charlie Kelly and sold by their company called MountainBikes (later changed to Fisher Mountain Bikes then bought by Trek, still under the name Gary Fisher, currently sold as Trek's "Gary Fisher Collection"). The first two mass-produced mountain bikes were sold in the early 1980s: the Specialized Stumpjumper and Univega Alpina Pro. In 1988 The Great Mountain Biking Video was released, soon followed by others. In 2007 Klunkerz: A Film About Mountain Bikes was released, documenting mountain bike history during the formative period in Northern California. Additionally, a group of mountain bikers called the Laguna Rads formed a club during the mid eighties and began a weekly ride, exploring the uncharted coastal hillsides of Laguna Beach, Ca. Industry insiders suggest that this was the birth of the freeride movement, as they were cycling up and down hills and mountains where no cycling specific trail network prexisted. The Laguna Rads also hold the longest running dowhill race once a year since 1986.
At the time, the bicycle industry was not impressed with the mountain bike, which many regarded as a short-term fad. In particular, large manufacturers such as Schwinn and Fuji failed to see the significance of an all-terrain bicycle and the coming boom in 'adventure sports'. Instead, the first mass-produced mountain bikes were pioneered by new companies such as MountainBikes (later, Fisher Mountain Bikes), Ritchey, and Specialized. Specialized was an American startup company that arranged for production of mountain bike frames from factories in Japan and Taiwan. First marketed in 1981, Specialized's mountain bike largely followed Tom Ritchey's frame geometry, but used TiG welding to join the frame tubes instead of fillet-brazing, a process better suited to mass production and which helped to reduce labor and manufacturing cost. The bikes were configured with 15 gears using derailleurs, a triple chainring, and a cogset with five sprockets.
1990s–2000s Throughout the 1990s and first decade of the 21st century, mountain biking moved from a little-known sport to a mainstream activity. Mountain bikes and mountain bike gear, that was once only available at specialty shops or via mail order, became available at standard bike stores. By the mid-first decade of the 21st century, even some department stores began selling inexpensive mountain bikes with full-suspension and disc brakes. In the first decade of the 21st century, trends in mountain bikes included the "all-mountain bike", the 29er and the singlespeed. "All-mountain bikes" were designed to descend and handle well in rough conditions, but still pedal efficiently for climbing, and were intended to bridge the gap between cross-country bikes and those built specifically for downhill riding. They are characterized by 4–6 inches (100–150 millimetres) of travel. 29er bikes are those using 700c sized rims (as do most road bikes), but wider and suited for tires of two inches (50mm) width or more; the increased diameter wheel is able to roll over obstacles better and offers a greater tire contact patch, but also results in a longer wheelbase, making the bike less agile, and in less travel space for the suspension. The single-speed is considered a return to simplicity with no drivetrain components or shifters, but thus requires a stronger rider.
Following the growing trend in 29-inch bikes (29ers as stated above), there have been other trends in the mountain biking community involving tire size. One of the more prevalent is the new, somewhat esoteric and exotic 650B (27.5 inch) wheelsize, based on the obscure wheel size for touring road bikes. Another interesting trend in mountain bikes is outfitting dirt jump or urban bikes with rigid forks. These bikes normally use 4–5" travel suspension forks. The resulting product is used for the same purposes as the original bike. A commonly cited reason for making the change to a rigid fork is the enhancement of the rider's ability to transmit force to the ground, which is important for performing tricks. In the mid-first decade of the 21st century, an increasing number of mountain bike-oriented resorts opened. Often, they are similar to or in the same complex as a ski resort or they retrofit the concrete steps and platforms of an abandoned factory as an obstacle course, as with Ray's MTB Indoor Park. Mountain bike parks which are operated as summer season activities at ski hills usually include chairlifts which are adapted to bikes, a number of trails of varying difficulty, and bicycle rental facilities.