Is Stephenson County, IL in a flood zone?
FEMA's National Risk Index puts Stephenson County's flood hazard at the 77.9th percentile nationally — a middling flood hazard by national standards — driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about 1.3 times a year. This describes the county, not any one street — FEMA only publishes exact parcel zones through a live map service.
Mandatory flood insurance compliance in Stephenson County
Out of 308 homes FEMA counts inside Stephenson County's mapped flood zone, 29 carry the flood policy federal law requires there — 9.4% compliance, short of full coverage. Across all residential structures in Stephenson County, not just the ones FEMA mandates, 0.3% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
Where Stephenson County ranks
Stephenson County sits at rank 725 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 1134 of 3144 by population (1 is biggest). Stephenson County, Illinois covers 564.247 square miles and counts roughly 43,088 residents.
Checking a specific address in Stephenson County
Across all of Stephenson County's 17,287 residential structures, 48 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed Stephenson County's numbers. The guide to what the Special Flood Hazard Area actually means explains why the mandatory-insurance rule exists and who it applies to.