Oh, no?
Five states currently conduct all elections entirely by mail: Colorado, Hawaii, Oregon, Washington and Utah.
At least 21 other states have laws that allow certain elections to be conducted by mail.
States that permit counties to opt into conducting all elections by mail:
California: Any county may conduct any election as an all-mail election following statutory guidelines. (Cal. Elec. Cde §§4005-4008).
Nebraska: Any county of less than 10,000 inhabitants may apply to the secretary of state to mail ballots for all elections in lieu of establishing polling places (Neb. Rev. Stat. §32-960).
North Dakota: Counties may conduct any election by mail. (North Dakota does not require voter registration ahead of the election) (ND Cent. Code §16.1-11.1-01 et seq.)
States that permit some elections to be conducted by mail:
Alaska: Elections that are not held on the same day as a general, party primary or municipal election (Alaska Stat.§15.20.800)
Arizona: A city, town, school district or special district may conduct elections by mail (Ariz. Rev. Stat. Ann. §16-409, §16-558)
Florida: Referendum elections at the county, city, school district or special district level (Fla. Stat. §101.6102)
Kansas: Nonpartisan elections at which no candidate is elected, retained or recalled and which is not held on the same date as another election (Kan. Stat. Ann. §25-432)
Maryland: Special elections not held concurrently with a regularly scheduled primary or general election (Md. Election Code §9-501)
Missouri: Nonpartisan issue elections at which no candidate is elected, retained or recalled and in which all qualified voters of one political subdivision are the only voters eligible to vote (Mo. Rev. Stat. §115.652 et seq.)
Montana: Any election other than a regularly scheduled federal, state, or county election; a special federal or state election, unless authorized by the legislature; (MCA 13-19-101 et seq.)
Wyoming: Counties may decide to conduct special elections not held in conjunction with a primary, general or statewide special election entirely by mail (Wyo. Stat. 22-29-115)
States that permit certain jurisdictions or portions of a jurisdiction to be designated as all-mail based on population:
Idaho: A precinct which contains no more than 140 registered electors at the last general election may be designated by the board of county commissioners a mail ballot precinct no later than April 1 in an even-numbered year (Idaho Code §34-308)
Minnesota: Elections conducted by a municipality having fewer than 400 registered voters on June 1 of an election year and not located in a metropolitan county (Minn. Stat. §204B.45)
Nevada: Whenever there were not more than 20 voters registered in a precinct for the last preceding general election (Nev. Rev. Stat. §293.213)
New Jersey: A municipality with a population of 500 or fewer persons, according to the latest federal decennial census, may conduct all elections by mail (NJRS §19.62-1)
New Mexico: A county may designate a precinct as a mail ballot election precinct if it has fewer than 100 voters and the nearest polling place is more than 20 miles from the precinct boundary in question (N. M. Stat. Ann. § 1-6-22.1)
https://www.ncsl.org/research/elections-and-campaigns/all-mail-elections.aspx
