In today's lecture, we'll discuss the history of the bicycle. The first pedal-powered bicycle was invented in the 1830s by Kirkpatrick MacMillan, a Scottish blacksmith. However, it wasn't until the 1880s that the safety bicycle, with two equal-sized wheels and a chain drive, became popular. This design made cycling much safer and more accessible, especially for women. By the early 20th century, bicycles had become a primary mode of transportation in many cities, before the rise of automobiles. Interestingly, the bicycle's popularity declined after World War II, but it saw a revival in the 1970s due to environmental concerns and the oil crisis.