On December 1, 1955 Rosa Parks boarded the Montgomery City bus to go home from work. She was a 42-year-old African American woman who worked as a seamstress. Parks sat near the middle of the bus, just behind the ten seats that were reserved for the whites. The bus was full, and when a white man entered, the bus driver asked her and three other blacks to give up their seats. Parks refused to move. This action was not pre-planned, although her previous civil rights involvement was an obvious influence. She was arrested and convicted of violating the laws of segregation. During her court case, a boycott broke out within civil rights activists in the bus system. Since blacks made up about 75% of the bus riders in Montgomery, the boycott was an economic threat. The boycott lasted 381 days and in December 1956, the U.S. Supreme Court ruled that the segregation law was unconstitutional and the Montgomery buses were integrated.