This is Cicindela limbalis, the green-margined tiger beetle. It's very similar to the purple tiger beetle, Cicindela purpurea, which shares much of its range. The curve of the middle spot/stripe is more sharply angled in the former, like in this specimen.
C. limbalis prefers moist, steep clay soil, like that found near lakes and rivers. This is why it is also known as the common claybank tiger beetle. C. purpurea prefers upland habitats, forest clearings, and places with shale-based soil. This one, and many like it, was found at Sweet Briar Lake in Morton County, North Dakota.