More than 4.1 million people visited Yosemite in 2015, the first time in history the park has eclipsed four million visitors in a year, according to new statistics from the National Park Foundation.
More than 90 percent of Yosemite visitors arrive by car, often creating traffic jams, especially in Yosemite Valley during weekends in the summer, when most lots fill by noon. Summer campsites in Yosemite Valley are often snatched up months in advance, within minutes of becoming available.
But summer traffic has been a problem for years, and the main reason for Yosemite's record year in 2015 was the drought and a corresponding rise in visitation during winter, spring and fall.
Yosemite is one of the America's most popular national parks. It tends to see the most visitors during dry, warm months. Last year, most of the year was dry and warm.
For example, in March of last year, when visitors could hike to the top of Yosemite Falls due to lack of snow, about 195,000 people visited the park, roughly 40 percent higher than the average from the prior 20 years.
This chart shows annual Yosemite visitation each year since 1906.