Oregon County Clerk Gary Hensley said polls will open at 6 a.m. and close at 7 p.m.
The only contested local race on the Democratic ballot will be for Oregon County treasurer.
Oregon County Treasurer Laurel Johnson is challenged in the primary by Kim Hollis. There are no Republicans or Libertarians in this race. The winner Aug. 8 will go to the November election unopposed.
Johnson has been treasurer the past 16 years. She has served four terms.
Hollis has worked in the Oregon County Clerk's office for 13 years. She works closely with the state elections division under the Secretary of State's Office.
Hollis and her husband David have lived in the Thayer area 29 years. They have two children, Rodney and Melanie, and three grandchildren.
The only contested local race on the Republican ballot will be for the 37th Circuit judge seat. Candidates are Richard Moore and David Paul Evans
The only other local issue that will appear on the ballot is Proposition 1. The Koshkonong School District is asking voters to authorize an increase in the district's operating tax levy by 78 cents per $100 assessed valuation.
Patrons in the Oregon-Howell School District will be asked to vote yes or no on the issue.
There is also one state constitutional amendment on the ballot, Constitutional Amendment 1.
The amendment would reinstate the existing 1/10-percent sales and use tax for 10 years. The tax funds soil and water conservation programs as well as the operation of state parks and historic sites.
Backers say the tax would generate approximately $82 million annually for soil and water conservation efforts in the state as well as support the operation of the state park system.