circulated commonly into the '40s & somewhat into the '50s. I found a 1903 Indian at an elementary school built in 1952 (the area was previously rural).
Part of the problem is places like parks may be relandscaped frequently with lots of fill dirt. I remember in the '70s I would find lots of Indian cents at some old places & few or none at other old places. It's the fill dirt thing, pretty sure. I once got some annual reports from park districts & they said things like "due to erosion, 8 inches of fill dirt was added to Island Park". Once I saw a school where the entire front yard was excavated to a depth of several feet or more, got to feel sorry for whoever detected there after that.
Besides fill dirt, other park renovations bury the old stuff where we can't get it: asphalt parking lots, asphalt or concrete basketball courts, concrete around picnic tables, newer park buildings sitting on old coins, volleyball pits or beaches where they take away old dirt & replace it with soft sand, etc.
Rivers & oceans deposit silt atop old coins or carry them away. And those places where the old coins were shallow were heavily detected in the '70s. Hope I haven't discouraged anyone with these comments. HH, George (MN)