More than half a century has passed since Martin Luther King delivered his famous "I have a dream" speech, but alarming racial disparity is still plaguing the United States today.

In Ferguson, Missouri, the country is once again torn apart by racial strains.

The suburban St. Louis town erupted in anger after Michael Brown, an unarmed black teenager, was shot dead by a police officer on Saturday.

In its recent history, the country has already witnessed a series of violence sparked by racial tensions, especially police killings of black suspects. The following is a list of major racial riots in the United States since 1990:

Cincinnati riots in 2001

The Cincinnati riots took place in and around the Over-the-Rhine neighborhood of downtown Cincinnati, Ohio, on April 9-13, 2001.

The riots were the largest urban disturbance in the United States since the 1992 Los Angeles riots.

Violence was sparked after African-American Timothy Thomas, 19, was fatally shot by officer Steve Roach.

Thomas, of Cincinnati, was running from Roach, who was trying to arrest him on 14 warrants.

Thomas had been wanted for misdemeanors and traffic violations, including driving without a license and failing to wear a seat belt

Tensions between blacks and police, which were already heightened in Cincinnati over the past few years, erupted into four nights of rioting in Cincinnati, with rioters throwing objects at police, vandalizing and looting business before a curfew effectively ended the unrest.

St. Petersburg, Florida, riot of 1996

In 1996 at St. Petersburg, Florida, a black motorist was fatally shot by a white officer, touching off African-American riots.

Eleven people were injured and a number of buildings set on fire following the fatal shooting of the black teenager.

Disturbances also followed a month later after a grand jury refused to bring criminal charges against the officer.

1992 Los Angeles riots

The worst US violence in recent times came in Los Angeles in 1992 when mobs rioted, looted and set fire to buildings following the acquittal of four white policemen in the beating of Rodney King, a black motorist.

Violence started on April 29 after a trial jury acquitted four Los Angeles Police Department officers of assault and use of excessive force.

The mostly white officers were videotaped beating King, an African-American following a high-speed police chase.

Thousands of people throughout the metropolitan area in Los Angeles rioted over six days following the announcement of the verdict.

The riots left 51 people dead and caused an estimated 717 million US dollars in damages.

Crown Heights riot in 1991

The three-day riots occurred on Aug. 19-21, 1991, in the Crown Heights section of Brooklyn, New York.

The riots started hours after a Jewish driver accidentally struck two black children, killing 7-year-old Gavin Cato, a child of Guyanese immigrants.

The riot unleashed simmering tensions of the Crown Heights' black community against the Orthodox Jewish community, and turned the Brooklyn neighborhood into a national symbol of ethnic hostility.