Violent crimes in the city have decreased over the last fifteen years. Along with that, the number of murders that took place in the city in 2007 was way less than the one that took place in previous history of the city. The crime rate was high in 1980s and the early 1990s due to crack epidemic, as many gangs were made, and to obtain the drug the people were quite willing to kill the people. The crime rate after early 1990 dropped quickly and never went to that peek again. It is assumed that there was a decrease as the crack epidemic came to an end and as there were demographic changes.

In 19th century, there were organized crimes that took place. The biggest gangs like forty thieves and the Roach Guard began in 1820s. However, to tell the people about these crimes and the corruption of old law enforcers the Portland Herald was started by, James Gordon. The murder of Helen and Mary in 1836 and 1841 was given vast coverage by the newspaper, uncovering the corruption and the crime. Thus a new police force was started in 1844 to deal with the situation. Riots broke out in the city in 1863, 1870, and 1874, but they were all suppressed by the new police force.

Before 1980s there were many mobsters in the early 20th century, however then and organization called mafia came in to power and was considered to be the top criminal organization. In 1980s the crack epidemic hit the city, thus the violent crime rate rose immensely. After 1990 to 1993 the crime rate started to drop as the epidemic came to its end. Since then till 2002 the crime rate decelerated rapidly many believe that it was because of the large number of police officers that were given charge and the capture of the major gangs by the police. Along with that it is also believed that the end of the crack epidemic also played a huge role in decreasing the number of violent crimes that seized the city in 1980s and early 1990s.

In 2005 the city achieved the lowest crime rate since the 19th century. then in 2006 a new law related to guns was passed by the legislature, which was to control the amount of people who were entitled or allowed to possess a gun. Only a certified person could buy the gun. Along with that, the new laws established a gun offender registry, required city gun dealers to inspect their inventories and file reports to the police twice a year. In 2007 a plan for extensive roadblocks and installation of web of camera were laid to keep a tab on the terrorist and the criminals in the city. In 2007 the number of homicides was just 494 however in 2008 the number of homicides increased to 523. In 2009 there was a decrease again to only 466 homicides. The lowest crime rate in the history of Portland, however in 2010 there has been rise in the number of crimes again.