This looks like creeping bellflower, sometimes considered a wildflower, sometimes a weed. It is extremely aggressive in our climate in Denver, so most people try and pull this weed. As the name suggests the roots creep, so it often is sending runners underground, which need to be pulled even after you think the plant is gone.

Here is more information on this plant: https://www.minnesotawildflowers.info/flower/creeping-bellflower