John Shields, who shepherded grocer Trader Joe’s through a major national expansion, died Oct. 31 after a long illness. He was 82. The Thousand Oaks resident took over what was just a California chain from founder Joe Coulumbe in 1988 and ran it for 13 years. By the time he stepped down in 2001, Shields had transformed it into a chain with sales topping $2 billion. Shields was born in Illinois and studied European history and earned an MBA from Stanford. He spent much of his career in retail, first with Macy’s Inc. and then at Mervyn’s before retiring in 1987. But he didn’t stay inactive for long when Coulumbe, his fraternity brother in college, asked him to help out as a consultant at Trader Joe’s. Coulumbe, who had operated other grocers, hit upon the idea of a specialty retailer featuring unusual and discounted gourmet items when he opened the first Trader Joe’s in Pasadena in 1967. There were only 27 outlets when Shields started helping Coulumbe out with the business, and he soon agreed to become chief executive. Under his leadership, the company opened its first store out of California in Arizona in 1993 and the first East Coast stores in the Boston suburbs of Cambridge and Brookline in 1996. By the time he retired again in 2001, there 174 outlets nationwide. Today, Trader Joe’s has about 420 stores in nearly 40 states. It has been owned by the Albrecht Family Trust in Germany since 1979. Shields is survived by two sons, two daughters and five grandchildren.