George M. Houser, shown here at his home in Rockland County, N.Y., died Aug. 19 at 99. (Joyce Dopkeen/The New York Times)

George M. Houser, a white Methodist minister who helped lead an interracial bus trip across the segregated South in 1947, an act of nonviolent resistance that years later inspired the better known Freedom Rides that stirred the civil rights movement, died Aug. 19 in Santa Rosa, Calif. He was 99.

He had congestive heart failure, said his son Steven Houser.

Rev. Houser was a pacifist and civil rights activist who advocated racial equality across decades and continents. His seminary studies were interrupted by one of his first acts of peaceful protest: He declared himself a conscientious objector and refused to register for the draft during World War II. For that offense, he spent a year and a day in jail, his son said.

As a young activist, Rev. Houser joined the Fellowship of Reconciliation, an organization promoting peace and social justice. He later joined other black and white activists in founding the Congress of Racial Equality, or CORE, in 1942.

CORE became — along with the National Association for the Advancement of Colored People, the Southern Christian Leadership Conference and the Student Nonviolent Coordinating Committee — a key institution in the movement for civil rights.

Among CORE’s most dramatic early actions was the bus trip designed in large part by Rev. Houser and Bayard Rustin, the activist who later became a chief organizer of the 1963 March on Washington.

They envisioned the trip shortly after the landmark 1946 U.S. Supreme Court ruling in the case of Irene Morgan, a black woman who was ordered to surrender her seat to a white person on a bus en route from Virginia to Maryland. Years would pass before the arrest of Rosa Parks, who in 1955 refused to give up her seat on a city bus in Montgomery, Ala.

In Morgan v. Virginia — argued by future justice Thurgood Marshall, among other lawyers — the court ruled segregation on interstate transportation to be unconstitutional. Enforcement of the ruling was uncertain, however, particularly in the Jim Crow South.

Along with Rustin, Rev. Houser set out to test compliance with the ruling by organizing a group of 16 travelers, including eight blacks and eight whites, on a trip across several Southern states.

Rev. Houser regarded the issue of segregated transit as one of fundamental importance. It “touched virtually every black person, was demeaning in its effect and a source of frequent conflict,” he once observed, according to the book “Freedom Riders: 1961 and the Struggle for Racial Justice” by historian Raymond Arsenault.

Rev. Houser and Rustin laid the groundwork for the trip by arranging the route and recruiting NAACP and other activists to help the riders in case of difficulty. It was agreed that only men, including Rev. Houser and Rustin, would participate, because mixing sexes as well as races might be too dangerous. They would travel across the states of the upper South but not venture into the Deep South, where they feared their demonstration might elicit severe reactions.

The trip — named the Journey of Reconciliation — took place in April 1947, departing from and ending in Washington. Black participants, when asked to move from the front to the rear of the bus, were instructed to calmly respond, “As an interstate passenger, I have a right to sit anywhere in this bus. This is the law as laid down by the United States Supreme Court.”

They were promised that, in the event of arrest, the NAACP would assist them. “If you happen to be arrested, the delay in your journey will only be a few hours,” they were assured, according to Arsenault’s book. “The value of your action in breaking down Jim Crow will be too great to be measured.”

According to CORE records cited in Arsenault’s book, the two-week trip resulted in 26 tests of compliance with the court’s ruling, 12 arrests and one act of violence. The group’s efforts did not receive widespread media coverage, but they became the model for the Freedom Rides, which ventured farther into the Deep South in 1961.

Beginning in the 1950s, Rev. Houser dedicated much of his activism to the anti-colonial and anti-apartheid movements in Africa. The South African government long barred him from the country. He met with Nelson Mandela after the anti-apartheid leader was released from 27 years in prison and, in 2010, received a medal from South African President Jacob Zuma.

George Mills Houser was born in Cleveland on June 2, 1916. His father was a Methodist minister. George spent part of his childhood in the Philippines and accompanied his father on pastoral assignments in New York, California and Colorado.

He received a bachelor’s degree in social science from the University of Denver in 1938 before enrolling at Union Theological Seminary in New York. After his jail sentence, he completed his divinity degree at Chicago Theological Seminary in 1942.

In recent years, Rev. Houser appeared on PBS programming that featured his work. He lived for many years in Pomona, N.Y., before moving to California, where he resided at a Quaker eldercare community.

Survivors include his wife of 73 years, the former Jean Walline, of Santa Rosa; four children, Martie Leys of Cotati, Calif., David Houser of Stoughton, Wis., Steven Houser of Grand Rapids, Mich., and Thomas Houser of Colorado Springs, Colo.; nine grandchildren; and eight great-grandchildren.

In a 2007 interview with the New York Times, Rev. Houser reflected on his life in activism and said he believed that “one step is enough and you take it, as long as you have faith you’re doing the right thing to begin with.” Two years later, more than six decades after the Journey of Reconciliation, a memorial was erected in Chapel Hill, N.C., where Rustin and others were arrested and later ordered to a chain gang.

Rev. Houser was there to see the memorial unveiled and remarked, “It’s kind of a way of saying, ‘We’re sorry it happened,’ isn’t it?”