Short answer. The highest annual average 30-year fixed mortgage rate in U.S. history was 16.63% in 1981, set during the Federal Reserve's anti-inflation campaign under Chairman Paul Volcker.
The Freddie Mac Primary Mortgage Market Survey began in 1971. The annual peak in the 50-year series was 16.63%, recorded in 1981. The weekly peak was higher still: 18.45%, the week of October 9, 1981.
Why did rates reach 16%+?
The U.S. entered the late 1970s with double-digit consumer-price inflation — a function of the 1973 OPEC embargo, the second oil shock of 1979, and a decade of accommodative monetary policy. Federal Reserve Chairman Paul Volcker, appointed in August 1979, raised the federal funds rate to a peak of 19% by mid-1981. Mortgage rates followed.
How long did rates stay above 10%?
Annual averages stayed above 10% from 1979 through 1990 — twelve consecutive years. The decade's range was 10.13% (1990) to 16.63% (1981).
Pre-1971 — what about earlier?
Reliable national 30-year fixed mortgage data does not exist before the PMMS series began. Estimates from FHA and VA loan documentation suggest 30-year fixed rates of roughly 5.5–6.0% through the mid-1960s, climbing into the 7–8% range by the early 1970s.
Today's context
The 2024 annual average was 6.84%. While historically that's not extraordinary — anything below the 1979–1990 range is below average for the modern series — the absolute payment burden is now record-high because home prices are at all-time highs.
Sources
U.S. Census Bureau Survey of Construction; National Association of Realtors Existing Home Sales report; Freddie Mac Primary Mortgage Market Survey; National Bureau of Economic Research Business Cycle Dating Committee.