Michael Nagle/Bloomberg News

Walgreen, the nation’s largest pharmacy chain, is growing ever-larger.

Just two weeks after Walgreen did its biggest deal ever, buying a 45 percent stake in the British drugstore giant Alliance Boots for $6.7 billion, it announced a deal on Thursday morning to pay about $438 million for a collection of U.S. drugstores.

The 144 stores, mostly in the South, were purchased from the closely held Stephen L. LaFrance Holdings, and members of the LaFrance family, according to a statement from Walgreen. The stores, located across 7 states, operate under the brands USA Drug, Super D Drug, May’s Drug, Med-X and Drug Warehouse.

“This acquisition expands our business in an important region of the country,” Walgreen’s chief executive, Greg Wasson, said in a statement.

Even before the Alliance Boots transaction, a deal that will allow it to push into international markets, the Deerfield, Illinois-based Walgreen has been on an acquisition streak. Last year the company paid $429 million for drugstore.com and in 2010 it acquired the New York chain Duane Reade for $1.2 billion.

Thursday’s acquisition is a tiny one for Walgreen. (Factoid: The company is Walgreen; the stores are called Walgreens). The 144 stores had sales of about $825 million last year. In 2011, Walgreen posted $72 billion in sales that generated a profit of about $2.7 billion. It has about 250,000 employees.

For now, Walgreen said that it will continue to operate the stores under their current brand names but “decisions will be made over time regarding the best, most effective way to harmonize Walgreens and the acquired brands.”

Walgreen’s acquisition is a boon for Stephen LaFrance, a pharmacist who started his drug store business in 1968 with a single USA Drug store in Pine Bluff, Ark. In 1997, with only 15 stores, he grew his business by buying the much larger Super D, a chain with about 100 stores.

“I have loved every minute of my career these past 44 years, beginning as a pharmacist, then management and currently as owner and chairman,” Mr. LaFrance, who is 70, said in a statement. “From the bottom of my heart, I would like to thank everyone who has been a part of my success: from my vendors, bankers, partners, employees, family and most importantly to my customers.”