Mason County, IL: flood risk, in FEMA's own numbers
On FEMA's National Risk Index, Mason County scores at the 47.2th percentile for flood hazard, rated "Relatively Low" — below the national norm for flood hazard. The hazard here is driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about once every 1 years. That's a county-wide figure, not a per-address one — FEMA's parcel maps are a live lookup, not a bulk file.
Mandatory flood insurance compliance in Mason County
10.2% of the homes FEMA requires to carry flood insurance in Mason County — those inside the mapped Special Flood Hazard Area — actually have a policy in force: 37 policies against 362 mandated structures, which means a meaningful share of legally-required coverage simply isn't there. Looking beyond the mandated zone, 0.6% of all residential structures in Mason County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
Where Mason County ranks
Among the 3144 US counties FEMA scores for flood hazard, Mason County ranks 1722 — 1 being the highest hazard nationally — and 2252 by population among all 3144 counties covered here, where 1 is the largest. About 12,543 people live in Mason County, Illinois, spread over 539.352 square miles.
What to do next if you own or are buying in Mason County
42 of Mason County's 7,546 residential structures carry flood coverage of some kind, per FEMA's latest count — useful context, not a substitute for checking one parcel.
Where Mason County's figures come from
Every figure on this page traces to a named FEMA dataset, documented in the methodology guide. If you're unsure why any of this insurance requirement exists at all, the SFHA explainer covers it from first principles.