If you're at least 18 years old and planning to vote on Nov. 6, listen up: Voter registration deadlines are coming.

Forty-nine states and the District of Columbia require voters to register before casting ballots in local, state or federal elections. Registration deadlines vary, but the majority occur throughout October – and 19 of those deadlines are Tuesday. In many states, residents can register in person, by mail or online.

Here's what you need to know.

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The basics

U.S. citizens ages 18 and older who meet their state's residency requirements can register to vote by filling out a form. (Find your state's requirements here.) Most states allow online registration, but you can also register at your local or state board of elections office.

North Dakota is the only state that doesn't require registration before voting.

Most states also allow voters to cast their ballots before Election Day. Find out if your state does early voting here.

The big deadline dates

If you live in Alaska and Rhode Island, you've missed your chance: The two states have the earliest registration dates in the country, and the deadline was Sunday, Oct. 7 . Montana's in-person registration deadline was also Sunday, but residents can do late registration up to Election Day.

. Montana's in-person registration deadline was also Sunday, but residents can do late registration up to Election Day. Tuesday, Oct. 9 marks the voter registration deadline for 19 states. Those include Ohio, Florida, Kentucky and Indiana. For some states, like Louisiana and Utah, Oct. 9 is the deadline to register in person; voters can continue to register via mail or online.

marks the voter registration deadline for 19 states. Those include Ohio, Florida, Kentucky and Indiana. For some states, like Louisiana and Utah, Oct. 9 is the deadline to register in person; voters can continue to register via mail or online. Four more states also have deadlines this week. Missouri's deadline is Wednesday, Oct. 10 , Oklahoma's and North Carolina's are on Friday, Oct. 12 and Delaware's is Saturday, Oct. 13 . All three allow registration in person, by mail or online.

, Oklahoma's and North Carolina's are on and Delaware's is . All three allow registration in person, by mail or online. Tuesday, Oct. 16 is another popular deadline for states. It's the registration cutoff for Kansas, Maryland, New Jersey, Oregon and West Virginia. South Carolina follows close behind with an Wednesday, Oct. 17 deadline.

is another popular deadline for states. It's the registration cutoff for Kansas, Maryland, New Jersey, Oregon and West Virginia. South Carolina follows close behind with an deadline. Alabama, California and South Dakota residents must be registered by Monday, Oct. 22 .

. Closing out October, Colorado's registration deadline is Monday, Oct. 29. That's followed by Connecticut's on Tuesday, Oct. 30.

Check your state's voter registration deadline here.

States without online registration

Twelve states don't have online registration available for residents:

Arkansas

Maine

Michigan

Mississippi

Montana

New Hampshire

New Jersey

North Carolina

Oklahoma

South Dakota

Texas

Wyoming

Different deadlines for different methods

Some states have different deadlines depending on how voters choose to register.

Louisiana: In person registration ends Tuesday, but voters can register online through Tuesday, Oct. 16 .

. Massachusetts: The deadline to register by mail is Tuesday, Oct. 16 , but in person and online registration goes to Wednesday Oct. 17 .

, but in person and online registration goes to . Nebraska: Nebraskans can register by mail or online through Friday, Oct. 19 , but have until Friday, Oct. 26 to register in person.

, but have until to register in person. Nevada: Three different dates for three different methods. Nevada's mail registration ends Tuesday, and in person registration ends Tuesday, Oct. 16 . Voters wishing to register online have until Thursday, Oct. 18 .

. Voters wishing to register online have until . New York: Friday, Oct. 12 is the deadline for in person and online registration. For those mailing in voter registration forms, they have to be received by Oct. 12.

is the deadline for in person and online registration. For those mailing in voter registration forms, they have to be received by Oct. 12. Utah: Although Utah's mail registration ends Tuesday, voters have until Tuesday, Oct. 30 to register either in person or online.

to register either in person or online. Washington: The state's deadline for mail and online registration is Monday. In person registration goes until Monday, Oct. 29.

Election Day registration

These states allow in-person registration up to Election Day, but check their individual deadlines for mail or online registration: