Twitter user @realFrosst shows us that Kansas hasn't elected a Democrat to the US Senate since 1932(!), while Hawai'i has the longest streak of not electing any Republican senators, going back to 1970.
If you compare the same state across the two maps, you can get a sense of how competitive the state is in recent history.
Maine is notable as a technicality, due to independent Senator Angus King, who caucuses with the Democrats.
Most Recent Year Each State Elected a Democrat to the Senate
Most Recent Year Each State Elected a Republican to the Senate
