By at least one measure, Dollar General (DG 3.40%) is the biggest retailer in the country. The discount chain has more stores under its banner than any other retailer in the U.S. with more than 20,000 stores. No other retailer comes close.For a long time, Dollar General's strategy of blanketing rural parts of the country with discount stores and offering essential products and sundries at low prices in small pack sizes was a winning formula.From its IPO in 2009 to its peak in 2022, the stock gained more tha ...