Colorado passed a measure legalizing physician assisted suicide in the state Tuesday. Proposition 109, or the End of Life Options Act, passed by a margin of two to one. The law will allow terminally ill people with six months or less to live to purchase medicine that will end their lives. 

Five other states have physician assisted suicide laws on the books. Proposition 109 was modeled after Oregon's Death with Dignity Law, Colorado's local News9 reported. Oregon was the first state to legalize assisted suicide in 1997. 

"This is a historic day for all Coloradans, and an especially tremendous victory for terminally ill adults who worry about horrific suffering in their final days," said Barbara Coombs Lee, president of Compassion and Choices Action Network, a Denver-based group that backed the measure. "We congratulate Colorado for becoming the sixth state where more people have peace of mind at the end of life and fewer suffer unnecessarily." Funding for the bill's opposition was provided by Catholic organizations. 

Physician assisted suicide and euthanasia are often used interchangeably, though the two terms refer to different things. Assisted suicide refers to an act of death aided by a doctor but ultimately done by the patient himself, such as by taking physician prescribed medication. Euthanasia occurs when a doctor himself performs the act through a lethal injection or otherwise. 

RTR3Z7IK Actress Susan Hampshire joins supporters of a bill legalizing assisted suicide outside Parliament in Westminster, London, Jul. 18, 2014. A similar measure passed in Colorado Tuesday. Photo: Reuters

The first assisted bill was proposed in 1967 in Florida. The measure didn't pass but ignited the first debate on the subject. In the 1990's, euthanasia activist Dr. Jack Kevorkian put the term on the map when he helped more than 130 people end their lives. Assisted suicide is now legal in Oregon, Washington, Montana, Vermont, California and Colorado. The remaining states consider it illegal and in some cases it is punishable by up to 10 years in prison.