The historic presidential campaign between Barack Obama and Hillary Clinton ends today in Montana at 8 p.m. -- when polls here close.

Even if you aren't registered to vote, it's not too late cast your vote.

Since November of 2006, Montana has allowed same-day registration and voting on Election Day. Here's how it works:

Go to the elections office in your county. Usually, these are located in the county courthouse, but not always. The Montana Secretary of State's office maintains a complete list of all election office locations. You can find the list at the secretary's Web site: www.sos.mt.gov. Or you can call the office at 444-2034.

For Helena, it's at the City-County Building in the Clerk and Recorder's Office, 316 N. Park Ave Room 168.

You must bring some kind of identification. This can include a driver's license, a tribal identification card, student ID, utility bill or other current document that shows your name and address.

You will be given an absentee ballot, which can be completed at the office or taken home. The ballot must be returned by 8 p.m., when polls close.

If you are already registered, but in a different county than where you now live, you can still register and vote Tuesday. However, you will be given a provisional ballot and that ballot will not be counted until elections officials in both counties can verify that you did not vote in your old county of residence.

Bowen Greenwood, spokesman for Secretary of State Brad Johnson, said if you intend to register and vote on the same day, be prepared for lines. There's a lot going on at election offices on Election Day and "a finite number of people."

For registered voters, most of the 33 polling places in Lewis and Clark County will be open from 7 a.m. to 8 p.m.

A handful of rural polls -- in Canyon Creek, Wolf Creek, Dearborn, Craig and York -- are open only from noon to 8 p.m.

Lewis and Clark County elections supervisor Marilyn Bracken noted that while late registration is allowed until 8 p.m. at the City-County Building, absentee voting is closed, so anyone who's already registered needs to go to their specified polling place.

She also noted that voters are required to bring identification to the polls, with a driver's license or voter registration card preferred.

A list of polling places is available through the county's Web site at www.co.lewis-clark.mt.us. Citizens with additional questions about where to vote or other questions about the election can call the county elections office at 447-8336, 447-8338 or 447-8339.

Reporter John Harrington contributed to this article.