
Brian B. answered 08/22/19
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The "Hopewell people" were a wide network of various local Native American cultures, spread all along the Great Lakes, Ohio River, and Mississippi River (and even east of the southern Mississippi as far as Florida). What they were notable for, from about 100 B.C. to around 500 A.D., was a wide and active trading network, where to this day archaeologists have discovered unified artistic traditions. The various Hopewell cultures tended to be semi-nomadic but partly agricultural. They tended to be largely peaceful -- the leaders weren't the sorts with the power to command armies or drive slave masses -- but they did show some stratification into a leadership class.
One of the things they're most famous for is their giant mounds, earth and clay that were sometimes big and round but sometimes sculpted into complex artwork. The 50-acre Octagon Mound, in Ohio, has even been speculated to be, like Stonehenge, a calendar and observatory, perhaps even following the moon's 18-year cycle higher and lower on the horizon.
I feel like their best-known "custom" is probably those mounds, but if so, "how did this custom aid in the regulation of their way of life?" is a weird question, because there simply isn't a firm understanding among scholars about what the mounds were mostly for. If their best-known custom is trade, though, it brought communication of information over long distance, shared artwork, shared resources, and a basis for peace.