The event often cited as the beginning of the modern civil rights movement is the Montgomery Bus Boycott, which began in December 1955. Sparked by Rosa Parks' arrest for refusing to give up her bus seat to a white passenger, the boycott aimed to challenge racial segregation on public transportation. Led by figures like Martin Luther King Jr., it lasted for over a year, ultimately leading to a Supreme Court ruling that declared segregation on public buses unconstitutional. The boycott ignited a broader civil rights movement, focusing on ending racial discrimination and promoting social justice in the United States.