Mortgage buyer Freddie Mac says the average rate on the 30-year loan fell to 3.53 percent. That's down from 3.56 percent last week and the lowest since long-term mortgages began in the 1950s.
The average rate on the 15-year mortgage, a popular refinancing option, declined to 2.83 percent, below last week's previous record of 2.86 percent.
The rate on the 30-year loan has fallen to or matched record low levels in 12 of the past 13 weeks.
Cheaper mortgages have contributed to a modest housing recovery. Home sales fell in June but were up from the same month last year. Home prices are rising in most markets.
Builders are putting up more houses than they have in nearly four years, a long-awaited recovery that could help energize the U.S. economy.
Low mortgage rates could also provide some help to the economy if more people refinance. When people refinance at lower rates, they pay less interest on their loans and have more money to spend. Many homeowners use the savings on renovations, furniture, appliances and other improvements, which help drive growth.
Still, the pace of home sales remains well below healthy levels. Many people are still having difficulty qualifying for home loans or can't afford larger down payments required by banks.
And the sluggish job market could deter some from making a purchase this year.
U.S. employers added only 80,000 jobs in June, a third straight month of weak hiring. The unemployment rate was unchanged at 8.2 percent, the government reported last week.
Slower job creation has caused consumers to pull back on spending.
Mortgage rates have been dropping because they tend to track the yield on the 10-year Treasury note. A weaker U.S. economy and uncertainty about how Europe will resolve its debt crisis have led investors to buy more Treasury securities, which are considered safe investments. As demand for Treasurys increase, the yield falls.
To calculate average rates, Freddie Mac surveys lenders across the country on Monday through Wednesday of each week.
The average does not include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.
The average fee for 30-year loans was 0.7 point, unchanged from last week. The fee for 15-year loans slipped to 0.6 point, down from 0.7 the previous week.
The average rate on one-year adjustable rate mortgages was unchanged at 2.69 percent. The fee for one-year adjustable rate loans also stayed the same, at 0.4 point.
The average rate on five-year adjustable rate mortgages dropped to 2.69 percent from 2.74 percent last week. The fee was unchanged at 0.6 point.