The measure completely changes how Oregon's justice system treats those who are found with personal-use amounts of hard drugs, the Associated Press reported.
Under Measure 110, they won't face criminal charges. Instead, they can choose to pay a $100 fine or go to an addiction recovery center, the AP reported.
The measure takes effect in early December, but the changes in penalties won't be implemented until Feb. 1. The addiction recovery centers will be funded by tax revenue from the state's legalized marijuana industry.
Making criminals out of drug users -- locking them up and burdening them with criminal records that make it hard to find employment and housing -- was not working, experts said.
About 3,700 fewer Oregonians per year will be convicted of felony or misdemeanor possession of controlled substances under the new measure, according to estimates by the Oregon Criminal Justice Commission.
The measure will also likely lead to significant reductions in racial and ethnic disparities in both convictions and arrests, the commission added.
"This is such a big step in moving to a health-based approach instead of criminal punishment, and we're devoting significant new resources to help Oregonians who need it," Janie Gullickson, co-chief petitioner of Measure 110, told the AP.
The measure has been approved by 59% of roughly 2 million votes counted so far, according to the Oregon secretary of state's office.
In 1973, Oregon became the first state to decriminalize marijuana possession, the AP reported.