Southern states used to only have one political party?

Is it appropriate to use the past tense when speaking of Southern states’ single-partyness?

Here’s a factoid that may startle:
[ul][li] In the 1940 Presidential election, Mississippi had by far the most lopsided vote of any state. 96% of Mississippian voters voted for the Democrat.[/li][li] In the 1944 Presidential election, Mississippi had by far the most lopsided vote of any state. 94% of Mississippian voters voted for the Democrat.[/li][li] In the 1964 Presidential election, Mississippi had by far the most lopsided vote of any state. 87% of Mississippian voters voted for the Republican. (That Republican lost in a landslide, winning only five Southern states and, barely, his home state.)[/li][li] In the 1972 Presidential election, Mississippi had by far the most lopsided vote of any state. 78% of Mississippian voters voted for the Republican.[/li][/ul]

Especially disconcerting is that Mississippi votes for the candidate less likely to support black civil rights despite that Mississippi has the highest portion of blacks of any state.