The west half of Interstate 35 through the Twin Cities. It is about 41 miles long and serves downtown Minneapolis and some western suburbs. However some parts of it are crappy and desperately need reconstructing. See Crosstown Commons. It needs help with interchanges with I-94 and I-494/MN 5 as well. In the future it may even need help with its interchange with I-694.
Unless absolutely necessary, take I-35E through the Twin Cities instead of I-35W.