Charles Walgreen III, who expanded his grandfather’s drugstore chain into an $18 billion-a-year company by 1999 when he stepped down as chairman, has died. He was 80.

He died Sept. 26 at his home in Lake Forest, Illinois, according to a statement from Deerfield, Illinois-based Walgreens Boots Alliance Inc. No cause was given.

He led Walgreen Co. as chief executive officer starting in 1971, adding the post of chairman in 1976. He stepped down as CEO in 1998 and retired as chairman the following year. During his tenure, the retailer reported 23 straight years of sales and earnings increases and quadrupled the number of stores to more than 2,400.

It was a big turnaround from 1970 when, according to trade publication Chain Store Age, Walgreen had “assumed many of the characteristics of the moribund A&P chain.”

The company was involved in so many unrelated activities — including Wag restaurants and department stores in Mexico — that drugstore managers “were sort of fighting for attention,” Charles Walgreen said, according to a 2000 story in Drug Store News.

Walgreen’s strategy was to refocus the chain on the drugstore business and modernize it, focusing on pharmaceuticals, health and beauty aids as well as photo service. He reconfigured the supply chain and upgraded the stores. Gone were the in-store optical centers and grocery aisles along with the company’s restaurants and south-of-the-border retailers.

By the 1980s, Walgreens stores were appearing in urban areas around the country, often concentrated with several stores in a relatively small area. The 1,000th store opened in 1984 and sales passed $10 billion in 1995.

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Walgreen in 2012 bought a 45 percent stake in Bern, Switzerland-based Alliance Boots Holdings Ltd. for $6.7 billion and in 2014 paid about $15.3 billion for the remainder of European pharmacy chain.