The National Conference of State Legislatures has this summary of the election results for state legislative races earlier this month. Republicans gained approximately 675 legislative seats. Republicans have clear majorities in both chambers of state legislatures for the first time since the 19th century in Tennessee, Alabama, and North Carolina. For the first time since the 19th century, there are more Republican state legislators than Democratic state legislators in the south.
Republicans also made huge gains in the state legislative elections in Maine and New Hampshire. Both houses of the New Hampshire went from Democratic majorities to super-majorities (more than 2/3rds) for Republicans. In Maine, the House went from 95 Democrats and 55 Republicans, to 77 Republicans, 73 Democrats, and one Green (whose ballot label was independent). In Minnesota, Republicans hold a majority in the State Senate for the first time since 1970.