The growth of the Gilmore family kept pace with the growth of the store. The two brothers were both married and had plenty of enthusiastic children who would help run the business through the twentieth century. John Gilmore was married to Mary Downey of Portage, and they had four children, daughters Ada, Jennifer, and Marjorie, and a son Robert. James Gilmore married Carrie Sherwood of Galesburg and had three sons, James, Irving, and Donald. John passed away in 1895 at the age of 43, and James followed him in death 13 years later in 1908 at the age of 51. The passing of the founding brothers of Gilmore's marked the end of an era, but not the end of the family or of the business that they loved.
In 1909 Carrie Gilmore, James's widow, secured property to expand Gilmore's into the large six-story structure that would dominate Burdick Street for the rest of the twentieth century. Despite some trouble raising money and skepticism about a woman handling such a large business, the structure was eventually built in 1910 and 1911. Two years later, in 1913, Carrie Gilmore married her neighbor Dr. W. E. Upjohn, and her sons began to move to the forefront in running the department store. Under the leadership of a new generation of Gilmores, the store continued to grow and prosper. Annual sales exceeded one million dollars for the first time in 1918. Along with the rest of the country, Gilmore's roared in the twenties and suffered under the depression in the thirties. However, strong leadership and a willingness to make changes like adding a parking lot for automobiles, and shifting emphasis from fabrics to ready-to-wear clothing, kept the store afloat through the tough times.