The modern "safety bicycle" came into being in the late 1800s, and was embraced by the public at the time... and is largely responsible for starting the evolution toward paved roads. The hoardes of cyclists demanded better-quality roads than the muddy thoroughfares that crossed the Fruited Plain up 'til that time. (That would be a hard pill to swallow, for many in our car-centric society nowadays.)
(For anybody interested in bicycle history, I recommend the book Bicycle: The History, by David V. Herlihy. It's comprehensive... and has lots of good photos and illustrations.)
Normally we think of the "mountain bike" as originating in the Bay Area, in the late-70s, early-80s. And indeed, that is when cycling enthusiasts first had the vision of a recreational bicycle ideally suited for trails and dirt-road travel.
However, it could be argued that "mountain biking" was already 80 years old by then. A couple weeks back, I was watching a show on PBS about Yellowstone National Park, and an old photo caught my eye - of a group of cyclists posed on the geologic features at Mammoth Hot Springs.
I did a bit of digging, and discovered The 25th Infantry Bicycle Corps.
They were organized in 1896. According to the Fort Missoula Museum website, "The Corps, consisting of eight black enlisted men, soon was riding in formation, drilling, scaling fences up to nine-feet high, fording streams, and pedaling 40 miles a day. Each bicycle carried a knapsack, blanket roll, and a shelter half strapped to the handlebar. A hard leather frame case fit into the diamond of each bicycle and a drinking cup was kept in a cloth sack under the seat. Each rider carried a rifle (first slung over the back, later strapped to the horizontal bar) and 50 rounds of ammunition."
As for the bikes... they had steel rims, tandem spokes, heavy-duty frame components, and weighed 32 pounds.
In 1897, they rode, essentially cross-country, from Missoula to St. Louis, a distance of 1900 miles, in 34 days. Provisions were dropped along the way at intervals, but they rode - or pushed, in the really gnarly stretches - the whole distance. It wasn't easy. They were "greeted triumphantly" at every whistle-stop along the way.
Frankly, I'm a little surprised that bicycles never caught on in certain situations, for military transportation. Probably too cheap.