Their time was largely devoted to Lyndon's political career. Lady Bird helped keep his Congressional office open during World War II when he volunteered for Naval service, and she was actively involved in the campaign for her husband's U.S. Senate seat.
LBJ once said that voters "would happily have elected her over me."
Worried about finances should his political career fail, they invested in radio station KTBC in Austin, which started a multimillion dollar media empire and made the Johnsons wealthy over time.
In 1955, it appeared that Lyndon Johnson, then the powerful Democratic leader of the Senate, might never reach the White House.
Johnson suffered a severe heart attack and Lady Bird helped to manage the staff until he could return to his post as Majority Leader.
During the Kennedy-Johnson 1960 campaign, Lady Bird was on the campaign trail non-stop, traveling 35,000 miles on behalf of the Democratic ticket.
As wife of the vice president under Kennedy, Lady Bird became an ambassador of goodwill, visiting 33 foreign countries.
As the new first lady, she established her own stamp of Southern hospitality on White House social events and built a reputation as a champion of environmental causes.
She immersed herself in efforts to beautify the capital and the nation.
"Ugliness is so grim," Johnson once said. "A little beauty can help create harmony, which will lessen tensions."
Deeply appreciative of America's natural beauty, Johnson recognized the opportunity to start a nationwide revitalization effort that involved restoring and protecting native plant habitats.
In the mid-1960s, she made headlines by planting bulbs and trees along roadsides and parkways and by calling attention to the growing crisis created by habitat and species loss.
She created the First Lady's Committee for a More Beautiful Capital and later expanded her program. Her work in Washington served as an introduction for the first major legislative campaign ever launched by a first lady - the Highway Beautification Act of 1965.
Known as "Lady Bird's Bill," it was the first milestone in a long list of accomplishments that protected the environment and had a dramatic impact on the American landscape.
Mrs. Johnson also took a highly active role in her husband's war-on-poverty program, the Great Society, notably advocating for the Head Start project for disadvantaged preschool children.
LBJ won his first full term in the White House in the 1964 election. His administration saw passage of major civil rights, anti-poverty, education and health-care legislation as part of the "Great Society" program.
But the escalation of U.S. involvement in the Vietnam War cast a shadow over his term. With nearly 500,000 U.S. troops battling the Viet Cong and North Vietnamese forces in March 1968, Vietnam forced Johnson to abandon thoughts of re-election.
Lady Bird agreed, wanting to retire and live quietly. The couple moved to their L.B.J. Ranch in Texas, where they lived quietly. The former president died in 1973.
Lady Bird Johnson's love for native wildflowers inspired her to create the National Wildflower Research Center in 1982 near Austin, Texas. It was renamed in her honor in 1998.
She remained outspoken on women's rights issues, calling the equal rights amendment, "the right thing to do." She was honored with the country's highest civilian award: the Medal of Freedom in 1977, and was given the Congressional Gold Medal in 1988.