well probably vermont. it's smallest to be in population terms, and it's even declining.
Wyoming is actually the smallest state population wise. It has 577,737 people to Vermont's 626,299 (according the Census Bureau's 2018 estimates). Both don't have that much going on, but Vermont's Governor has to run every two years so that sucks for whoever is in charge. Either way, both states have a smaller population than the District of Columbia.
Speaking of DC, it may even leapfrog Alaska in several years if it keeps up its high growth (16.73%) its had since 2010, with Alaska having grown only 3.83% in the same time period. DC only has ~35,000 fewer people than Alaska according to the CB's estimates for 2018.