It was 60 years ago today that a simple act of civil disobedience in the U.S. South sparked a civil rights movement.

On Dec. 1, 1955, Rosa Parks refused to give up her seat to a white man on a public bus in Montgomery, Ala.

Police arrested the seamstress for violating the city's racial segregation laws, which required black Americans to sit in the back of public buses and mandated they give up their seats to whites if the front seats were full.

Parks was fined $14 US for refusing the bus driver's order to move to the back of the bus.

Rosa Parks arrest

Rosa Parks, right, was arrested 60 years ago in Montgomery, Ala., after refusing to give up her seat on a bus for a white passenger. (Gene Herrick/Associated Press)

Parks's refusal precipitated a year-long boycott of Montgomery buses and galvanized a 26-year-old Baptist minister named Martin Luther King Jr.

The boycott ended 385 days after the incident when the Supreme Court struck down the Alabama and Montgomery laws as being in violation of the equal protection clause of the 14th Amendment of the U.S. Constitution.

Parks, who died in 2005 at 92, was among the first to ride the newly desegregated buses in 1956.

"Because Rosa Parks kept her seat, thousands of ordinary commuters walked instead of rode," President Barrack Obama said Tuesday in a statement. "Because they marched, our union is more perfect."

The anniversary of Parks's refusal is being commemorated across the U.S.

In Topeka, Kan., the bus system was offering free bus rides to the public on Tuesday, while Democratic presidential candidate Hillary Clinton was scheduled to be in Montgomery to speak in a church pastored by King during the boycott.