Jefferson County, Missouri
Everything a Jefferson County, Missouri voter needs in one place: registration, voter ID, absentee and early voting, and your sample ballot. Home to about 232,000 people, Jefferson County ranks 7th in population among Missouri's 115 counties. In Missouri, elections are run by local election authorities: the county clerk in most counties, or a board of election commissioners in several cities and counties.
Next Election
August 8, 2028
Voter Portal
Register Online
What's On My Ballot?
ID Requirements
Absentee / Early Voting
Registration Deadline
Register by the fourth Wednesday before an election.
Why Voting Matters
In Jefferson County, the people who show up to vote decide who represents everyone. The next election for Jefferson County voters is Missouri's state primary on August 8, 2028; local elections can come sooner, so check your local election office. Many Jefferson County jobs are in retail and restaurants and hospitality, so decisions about local businesses and tourism and small businesses hit close to home.
Jefferson County voters cast about 119,000 ballots for president in 2024, up about 2% from 117,000 in 2020. Compared with the county's roughly 182,000 adult residents, that works out to about 65%, above the statewide rate of about 61%.
That means roughly 63,100 adult residents did not cast a presidential ballot. Some are not eligible, but many are, and that is a lot of untapped power. If just one in 20 of them voted, Jefferson County would add about 3,160 voices, more than enough to decide a close local race.
Jefferson County covers about 657 square miles, with roughly 353 residents per square mile. The county is home to about 3.7% of Missouri's population.
ZIP codes in or partly in Jefferson County include 63010, 63012, 63015, 63016, 63019, 63020, 63023 and 63025, plus 21 more. Confirm your registration, read through your sample ballot before Election Day, and choose whether you will vote early, by mail or in person. Invite someone you know in Jefferson County to join you.
Voter Assistance Resources
Who runs elections in Jefferson County? In Missouri, elections are run by local election authorities: the county clerk in most counties, or a board of election commissioners in several cities and counties. For registration, polling places, early voting and absentee ballots, contact the Jefferson County local election authority (county clerk or board of election commissioners).
Statewide directory, Missouri Secretary of State elections division:
https://www.sos.mo.gov/elections/
See your sample ballot. Missouri Secretary of State elections division (voter lookup shows sample ballots):
https://www.sos.mo.gov/elections/
You can also preview a personalized ballot at Vote411.org.
To ask a question or report a problem at the polls, call or text Election Protection at 866-OUR-VOTE (866-687-8683), a free nonpartisan hotline. For help in Spanish call 888-VE-Y-VOTA (888-839-8682); for Asian languages call 888-API-VOTE (888-274-8683).
Voters with disabilities in Jefferson County can ask for an accessible voting machine, curbside voting where offered, and help from a person of their choice. If you run into barriers, contact Missouri Protection & Advocacy, Missouri's Protection and Advocacy agency, at (573) 893-3333. VoteRiders (844-338-8743) offers free help with voter ID.
Need a ride? Many local transit agencies and ride services offer free or discounted rides to the polls on Election Day, so check what is available before the next election. See our Missouri voter page for statewide options. Details can change, so confirm with the official election office.
Military and overseas voters can get help from the Federal Voting Assistance Program at 1-800-438-VOTE (8683) or fvap.gov.
Sign up to be an election worker
Election workers (often called poll workers) keep voting running smoothly in Jefferson County. Most are paid for their time, get free training, and help their neighbors cast their ballots. You can work a full day, a shorter shift, or help before Election Day. County and municipal election offices recruit and train their own workers, and the EAC's Help America Vote page links to yours. Find out how to sign up:
https://www.eac.gov/help-america-vote
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