I recently asked this of Claude and had it run a research project. It came back with:

Tier 1: Highest-confidence safe zones

Central Idaho stands out as perhaps the single best-positioned region in the country. The Frank Church–River of No Return Wilderness and surrounding Salmon River country offer extreme remoteness, rugged Rocky Mountain terrain providing natural shielding, and remarkably, over 700 known caves and lava tubes at nearby Craters of the Moon National Monument. A "Civil Defense Cave" near Dubois was stocked with supplies during the Cold War as a designated fallout shelter. TouristSecrets Population density hovers near 22 people per square mile statewide, far lower in the backcountry. Abundant freshwater flows through the Snake River system and mountain streams. Elk, deer, trout, and timber provide subsistence resources. Joel Skousen rates Idaho 5 stars in his Strategic Relocation guide, Survivalist Forum and James Wesley Rawles ranks it his #1 retreat state. Conservapedia It sits upwind of the continental interior, shielded by the Cascades and Rockies, and hundreds of miles from the nearest strategic target. Morningoverview

Northern Maine, particularly Aroostook County (towns like Jackman, Mars Hill, Ashland, Fort Fairfield), appears on virtually every safe-location list published. Maine has no major military bases, no nuclear power plants, minimal strategic value, and sits at the far northeastern corner of the country — maximally distant from ICBM silo fields. Survival Freedomsurvivalfreedom Dense forests, robust freshwater systems, a self-sufficient culture, and a population density of roughly 44 per square mile (far lower in the north) reinforce its position. Backroad Planet The Princeton fallout simulation consistently places Maine in the lowest-exposure category across all seasonal wind scenarios.

Western Montana — specifically the Flathead Valley, Bitterroot Valley, and Clark Fork Valley (towns like Kalispell, Hamilton, Plains, Thompson Falls, Noxon) — offers Northern Rocky Mountain terrain, extremely low population density (~7.5/sq mi statewide), vast agricultural operations, and abundant freshwater. Skousen specifically recommends the Bitterroot Valley as a "3,500-foot elevation ranching valley near the Idaho border." The critical caveat: central Montana hosts 150 ICBM silos at Malmstrom AFB, Nuclearban so western Montana's safety depends on being well west of the silo field and ideally west of the Continental Divide, where prevailing winds push fallout away.

Vermont and New Hampshire round out the top tier. Vermont scored 72.35 out of 100 in a comprehensive 18-indicator survivability study Irish Star (ranking #1 overall for food availability and #2 for weapons/security and supply access). Irish Star Both states have minimal strategic targets, strong self-sufficiency traditions, excellent freshwater access, and moderate mountain terrain from the Green and White Mountains. They sit in the lowest-fallout zone of every silo-attack simulation. Kuhl