20th Century
During most of the 20th century in the USA, except for a brief period of popularity during the Great Depression of the 1930s, bicycles were relegated to the status of children's toys.
US bike boom of 1965–1975: The period of 1965–1975 saw adult cycling increase sharply in popularity — with Time magazine calling it "the bicycle's biggest wave of popularity in its 154-year history" The period was followed by a sudden fall in sales, resulting in a large inventory of unsold bicycles. Seven million bicycles were sold in the U.S. in 1970. Of those, 5½ million were children's bikes, 1.2 million were coaster brake, balloon-tired adult bicycles, and only 200,000 were lightweight 3-speed or derailleur-equipped bikes. Total bicycle sales had doubled by 1972 to 14 million — with children's bikes remaining constant at 5½ million, adult balloon-tired bicycles falling to about 1/2 million, and lightweight bicycles exploding fortyfold, to 8 million. Time Magazine reported in 1971 that "for the first time since the 1890s, nearly one-half of all bicycle production" was "geared for adults."
The boom received a kick start in the mid 60s with the advent of the Schwinn Sting-Ray and other wheelie bikes. Sales reached 4 million units per year for the first time. At the height of the boom, in 1972, 1973, and 1974, more bicycles than automobiles were sold in the U.S.
Additional factors contributing to the U.S. bike boom included affordable and versatile 10-speed derailleur-geared racing bicycles becoming widely available, the arrival of many post-World War II baby boomers at adulthood and demanding inexpensive transportation for recreation and exercise, and increasing interest in reducing pollution. The 1973 oil crisis, which increased the cost of driving an automobile, making bicycle commuting a more attractive option, is commonly assumed to have propelled the bike boom, but in fact, bicycle sales had already peaked when the crisis struck in October, 1973.
As of 2008 some industry analysts see signs of surging bicycle popularity.
Read more about this topic: Bike Boom