When the U.S. Congress passed — and President Lyndon Johnson signed into law — the Immigration and Naturalization Act of 1965, the move was largely seen as symbolic, Lesley Kennedy wrote recently for History.com.

Democratic U.S. Sen. Ted Kennedy of Massachusetts said during Senate debate that the bill would not “flood our cities with immigrants. It will not upset the ethnic mix of our society. It will not relax the standards of admission. It will not cause American workers to lose their jobs.”

Johnson echoed that sentiment upon signing the bill on Oct. 3, 1965: “It does not affect the lives of millions … It will not reshape the structure of our daily lives or add importantly to either our wealth or our power.”

But the measure, which aimed to eliminate race and ethnic discrimination in immigration, ended long-standing national-origin quotas that favored immigrants from Northern and Western Europe. It led to a significant immigration demographic shift in America.

Read Lesley Kennedy’s complete story here for a look at the key changes brought by the act.

How the Immigration Act of 1965 Changed the Face of America