24 States with Voter Initiative and year adopted

Alaska 1959
*Arizona 1912
Arkansas 1909
*California 1911
*Colorado 1912
Florida 1972
Idaho 1912
Illinois 1970
Maine 1908
Massachusetts 1918
Michigan 1908
Mississippi 1992
Missouri 1906
Montana 1904
Nebraska 1912
Nevada 1904
*North Dakota 1914
Ohio 1912
Oklahoma 1907
*Oregon 1902
South Dakota 1898
Utah 1900
*Washington 1912
Wyoming 1968
*combined, these 6 states have over 60% of all initiative activity