The running of the bulls is first thought to have originated as a method to transport the bulls from the corral to the bullfighting ring. The tradition is believed to have been started in the 13th century and has continued as a regular event since 1542.
While the running of the bulls has taken place for hundreds of years, people did not actually start running in the event until sometime in the 1800s. The event begins on July 7th and takes place every day during the festival of San Fermin, the patron saint of Pamplona.
The modern-day running of the bulls is much different from the one that originated hundreds of years ago, as thousands of foreigners come to Pamplona every year to participate in the running of the bulls. Participants wear all white clothing and the traditional red sash and bandanna. Before the bulls are released, it is tradition for all runners to sing a traditional homage to St. Fermin and to ask for his guidance and protection during the event.
The running of the bulls was made famous outside of Spain because Ernest Hemingway wrote a detailed description of the event in his book, "The Sun Also Rises."