The Dallas Cowboys have become the first American sports franchise worth more than $2 billion US, according to Forbes magazine.

The NFL's most valuable team for the sixth consecutive year, the Cowboys saw their overall worth increase 14 per cent to $2.1 billion. That's about $1 billion higher than the average NFL team value, $1.11 billion, up 7 per cent.

New TV contracts, the collective bargaining agreement signed last year and lasting for a decade, and higher premium seating revenue contributed to the increases.

With new stadiums in the works for the Vikings and 49ers, their values skyrocketed. Minnesota had a 22 per cent increase to $975 million, while San Francisco moved up 19 per cent to $1.175 billion.

New England was second to Dallas in overall value at $1.635 billion.