For about 50 years before 1972, the rate of imprisonment in the United States was steady.

But in the 1960s, rising crime rates, urban riots and social tensions triggered tough-on-crime policies that would alter the size and racial composition of the prison system.

Here are major players in this movement and the role they played in satiating the public and political hunger for law and order.

Richard Nixon

First president to popularize the term “war on drugs.” Under his presidency, majority of funding goes toward treatment, rather than law enforcement.

Nelson Rockefeller

New York governor creates some of the harshest sentences for drug crimes. Under Rockefeller drug laws, penalty for possessing four ounces of cocaine or heroin or for selling two ounces is a mandatory prison term of 15 years to life. Today, nearly every state and the federal government have some form of mandatory sentencing.

Ronald Reagan

Prioritizes war on drugs, signing three massive drug bills in 1984, 1986 and 1988. Nancy Reagan’s “Just Say No” anti-drug campaign becomes centerpiece of drug war. Drug laws in 1986 create mandatory minimum penalties for drug offenses; creates 100-to-1 sentencing disparity between crack and powder cocaine.

By early 1990s, nearly 90 percent of crack prosecutions target non-whites. In 1995, the average federal prison term for a crack offense surpasses that for murder.

George H.W. Bush

Spends more money on drug war than every president since Nixon combined. Federal inmate population nearly triples to 80,259, mostly for drug crimes. Roughly 60 percent are Black or Latino. In 1991, Blacks in prison outnumber whites, even though Blacks make up 12 percent of the population.

Bill Clinton

Oversees most intensive incarceration boom in U.S. history, with federal incarceration rates during his term more than that of Bush and Reagan combined. By 2001, 645,135 more Americans are in jail than on Clinton’s inauguration day. Fifty-five percent are Black or Latino.

George W. Bush

As governor of Texas, Bush oversees execution of a record 152 people. After 9/11, Bush targets immigration policy in the name of national security; most of the legal infrastructure was put in place during Clinton era. U.S. Patriot Act of 2001 makes it easier for the government and law enforcement to access private information, detain immigrants and search homes and businesses.

Barack Obama

In August, Obama signs new law reducing the crack/powder cocaine disparity in sentences. He has also pledged to push for immigration reform. Justice Department files lawsuit to block Arizona’s tough new immigration law.