Over the course of the next six years, Elsie designed the interiors of many prestigious homes and clubs on both the East Coast and West Coast. She also worked on opera boxes, a dormitory, and a model home. By 1913, she had developed her business enough to take up an entire floor of offices on 5th Ave., complete with assistants, secretaries, and bookkeepers. In 1915, she received a commission by Henry Clay Frick, one of the richest men in America at the time. Previously he had lived at a chateau in Pennsylvania, while making millions monopolizing the coal industry. On his retirement, he moved to New York City, where he bought a block on 5th Ave., along with the building the NY public library had occupied, for around $2.5 million. He demolished the building, and hired Thomas Hastings to build a new home for him and his family. Sir Charles Allom, known for his work remodeling Buckingham Palace, was hired to decorate a number of rooms on the first floor of the home; Elsie was hired to decorate the second floor, which included the sleeping quarters, among other rooms. Though it is not known exactly how it was that she secured the job with Frick, it is possibly due to her reputation as one the best, if not the best, decorators of the time. Earning a commission for every piece of art or furniture she purchased for Frick, Elsie became a very rich woman. She continued to design interior spaces for a long list of prestigious clients, and wrote several books and articles. During World War I, she volunteered as a nurse in France, and it was not until nearly the end of her career that, at the age of 61, she married.