By running a custom search by birth date on the records in the Legislators Past & Present database, we found 26 instances where legislators 80 years or older were elected.
Rep. Willard Munger accounts for five of those times, as he was elected at age 80, 82, 84, 86, and 88. At 88, he was the oldest legislator ever elected. Rep. Bernie Lieder was the second oldest person to be elected, at 86 (he was also elected at age 84, 82, and 80).
Rep. John Hompe was the third oldest, elected in 1929 at age 85 (and also elected at age 83 and 81). Our record notes that in 1931, when he was 85, he was the oldest legislator in the United States.
Eleven members accounted for the 26 instances of someone 80 or older being elected.
What about the oldest freshmen legislators? Who were the oldest people to serve a first term in the Minnesota Legislature? Two people were first sworn in at age 79. R. Bruce Kennedy was elected to the House in 1950, and Thomas Lowe was elected to the House in 1936. Because we only have birth years for them, without the months and days, we don't know who was actually older.
Back to statehood, we have birth dates for 96% of all members who have served, but not all, so our data can't be perfect.