What is adverse possession and what elements must typically be proven for someone to claim ownership of land they do not legally own?

Adverse possession is a centuries-old common law doctrine (rooted in English law) that allows a trespasser to eventually gain legal title to land they occupy if they meet specific requirements for the statutory period, which ranges from 5 years in some states to 21 years in others. The elements typically required are: actual use and possession of the land, open and notorious (visible and obvious, not hidden), exclusive (not shared with the true owner), hostile or adverse (without the owner's permission), and continuous for the statutory period. Property owners can defeat adverse possession claims by granting the occupant permission (which destroys the hostile element), by posting 'no trespassing' signs, or by physically evicting the occupant during the statutory period.