Americans' wealth hit the highest level ever last year, according to data released Thursday, reflecting a surge in the value of stocks and homes that has boosted the most affluent U.S. households.

The net worth of U.S. households and nonprofit organizations rose 14% last year, or almost $10 trillion, to $80.7 trillion, the highest on record, according to a Federal Reserve report released Thursday. Even adjusted for inflation using the Fed's preferred gauge of prices, U.S. household net worth—the value of homes, stocks and...