Is Gregory County, SD in a flood zone?
FEMA's National Risk Index puts Gregory County's flood hazard at the 15.4th percentile nationally — among the lowest flood hazard in the country — driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about once every 2 years. That's a county-wide figure, not a per-address one — FEMA's parcel maps are a live lookup, not a bulk file.
Who actually carries the flood insurance FEMA requires
Gregory County is one of the counties where FEMA's own denominator for mandated flood-zone structures is missing, so no compliance rate is shown rather than a guessed one — the data quality guide covers how common this is. Across all residential structures in Gregory County, not just the ones FEMA mandates, 0% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
Gregory County against the rest of the country
Gregory County sits at rank 2692 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 2874 of 3144 by population (1 is biggest). Gregory County, South Dakota covers 1,014.95 square miles and counts roughly 4,110 residents.
Your street may differ from Gregory County's average
1 of Gregory County's 4,552 residential structures carry flood coverage of some kind, per FEMA's latest count — useful context, not a substitute for checking one parcel.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed Gregory County's numbers. See the data quality guide for why Gregory County, like hundreds of other counties, doesn't get a clean compliance percentage.