It's a good time to be a female entrepreneur.

Over the past 15 years, the number of female-owned businesses has increased more than 54% nationally, according to a study by American Express OPEN.

Between 1997 and 2012, the number of women-owned businesses grew at a pace that was 1.5 times the national average, according to the study. More than 8.3 million businesses--or 29% of all businesses--are now owned by women.

For the most part, the study found, the biggest growth has come in Southern states. States where woman-owned businesses had the fastest growth rates over that time period included Georgia (with 95% growth), North Carolina (83%), Mississippi (75%), and Texas (75%). One Western outlier was Nevada, which had a 92% surge in woman-owned businesses.

The lowest growth rates were in Alaska (11%), Iowa (21%), West Virginia (22%), Kansas (25%), and Ohio (25%).

But despite the high growth rates, the survey held some less cheery news for female entrepreneurs: Woman-owned businesses only contribute 4% of total U.S. business revenues--$1.3 trillion--and employ roughly 7.7 million people, or just 6% of total employment.