In wilderness parts of the US you are usually allowed, by law, to break into unoccupied cabins/homes in critical situations (eg blizzard, you're lost, etc). You're required to leave identification and contact info and pay for any damages and/or supplies used.

Often people just leave remote dwellings like that unlocked and stocked with supplies, sometimes with a signature book and/or donation box. For larger places some people even build a separate cabin next to the main house for travelers to use.