In January 1964, President Johnson was aware that almost one in every five Americans lived in poverty.
In his first State of the Union address, just weeks after taking office, he proposed a solution.
"And this administration today, here and now, declares unconditional war on poverty in America," he said, issuing his first salvo in the "war" that would take the form of new programs to improve nutrition, health care, education and job training.
"Our chief weapons in a more pinpointed attack will be better schools, and better health, and better homes, and better training, and better job opportunities," he said.
According to James Jones, who later became Johnson's chief of staff, the president wanted to complete the unfinished domestic agenda of previous Democratic Party presidents.
"Things such as Medicare, which [then-President] Harry Truman first proposed in around 1946-47, and nothing had been done on that," said Jones. "Things such as fair housing, which, again, went back to the Truman administration, and nothing had happened in 20 years."
When President Johnson and his wife toured impoverished areas in 1964, 19 percent of Americans lived in poverty. Today's figure is 15 percent, not good enough according to Michael Tanner, senior fellow at Washington's Cato Institute, a libertarian think tank.
"That's not a great deal when you consider how much money we've spent," he said. "If you want to reach back to 1964, we've spent maybe $15 trillion, and yet poverty seems to be pretty flat."
Critics in Congress say spending on poverty reduction programs is out of control, and the Republican-led House of Representatives recently voted to cut funding for the Food Stamp assistance program by about $4 billion a year.
Tanner also says the wide availability of welfare benefits reduces the incentive to work.
"Look, poor people are not lazy, but they're also not stupid," he said. "If you pay people more not to work than they could make by working, then chances are many of them are going to consider — think twice, at least — about working."
Still, Johnson's initiatives, despite their flaws, have lifted millions out of poverty, says Ron Haskins, a former White House and congressional advisor on welfare issues and co-director of the Center on Children and Families at The Brookings Institution, a Washington-based non-profit research organization.
"The general direction and the focus on poverty and some of the specific programs have been enormously successful," said Haskins. "The country is better off because Johnson did it."
Former aide Jones says the programs that arose from the War on Poverty were among Lyndon Johnson's top achievements.
"I think, now that history has had a 50-year look at his time, I think they're beginning to appreciate that he really was an outstanding president," he said.