Wendy's pretzel burger has been a success in test markets and could make its national debut later this year. Reuters

Wendy's had toppled Burger King's rein as the second biggest fast food chain, after McDonalds. The burger joint has surpassed Burger King's U.S sales for the first time since it was established in 1969, according to a report by research firm Technomic Inc.

Although Burger King has 7,200 locations in the U.S. over Wendy's 5,900, its 2011 sales totaled $8.4 billion under Wendy's $8.5 billion.

McDonalds, however, dwarfs both Wendy's and Burger king, totaling $34 billion in sales last year. Five Guys Burgers and Fries also featured in the research as a fast-growing chain in the U.S.

5 reasons why Wendy's may have beaten Burger King:

Price: Throughout the recession and beyond, Wendy's has managed to keep prices low. Their Everyday Value Menu offers items such as burgers, sandwiches, fries and wraps for just 99 Cents.

Menu: In trying to keep up with the fast growth of McDonalds. Wendy's has introduced new items to its menu, including premium fish and new burgers.

Remodeling Restaurants: Wendy's may be popular for its old-fashioned hamburgers, but the fast-food chain has spent the past two years modernizing and revamping their look, making it a more airy and inviting environment for its customers.

New Mission: In recent years Wendy's has been on a new mission to reinvent itself as a higher-end burger joint, introducing new items like Dave's Hot 'N Juicy burger.

Employees: As a part of the company's new mission, Wendy's CEO Emil Brolock has been working to raise the standard for employees.

Both Burger King and Wendy's have struggled in recent years, but Wendy's new strategy seems to be paying off with sales up 26 percent in the past five years. Burger King's sales have been flat in comparison.

Wendy's and Burger King used to be in the sales ranking for the top five restaurants in the U.S, but since 2006 Subway and Starbucks have taken over in second and third place. Subway sales have gone up 48 percent in the past five years and Starbucks sales are up by 30 percent, according to the Technomic report.

The research covers sales for the top 500 restaurant chains in the U.S and will be released on April. 13 according to the Associated Press.