WASHINGTON (AP) — Americans gave their credit cards a real workout this past holiday season.

The Federal Reserve said Friday that borrowing on credit cards rose by the largest amount in more than two decades in December.

Total U.S. consumer borrowing rose $22.1 billion in December, the central bank said. That was the biggest gain since July and nearly double the $11.8 billion increase in November.

The overall December surge was led by a $12.6 billion increase in the category that includes credit cards. It was the biggest one-month gain in credit card debt since a $19.5 billion increase in April 1998.

December’s jump came after a $2.9 billion decline in credit card borrowing in November.

The surge in credit card borrowing in December was another sign that retailers had a good holiday shopping season, although a growing share of those purchases are going to on-line retailers rather than brick-and-mortar stores.

Borrowing in the category that covers auto loans and student loans was up $9.4 billion in December, down from a $14.7 billion gain in November.

Consumer borrowing is closely watched for signals it can provide about Americans’ willingness to take on debt to finance consumer spending, which accounts for 70% of U.S. economic activity.

The overall increase of $22.1 billion pushed consumer credit to a record of $1.1 trillion. The Fed’s monthly credit report does not cover home mortgages or other debt secured by real estate such as home equity loans.