He faced a series of difficulties when his career decline

Sullivan got lonely and challenging as his prosperous years with Adler faded into a troubling memory. He grew apart from his successful brother Albert, an Illinois Central Railroad official who also resided in Chicago. The middle-aged Sullivan turned became a bit of a loner, turning to his work and trips to his vacation home in Ocean Springs, Mississippi, for solace. His 1899 union with Margaret Davies Hattabough did not provide him much long-term joy. Since there were problems with their partners from the start, they separated in 1906 and divorced in 1917 without having given birth to any children. Sullivan tried to save money by relocating to motels that were gradually less expensive as his salary dropped.

He was in dire problems by 1909 due to a lack of commissions; as a result, he was compelled to sell his belongings, including his library. Perhaps an equal loss was Elmslie's departure that year, who joined forces in Minneapolis with William Gray Purcell, an architect who had briefly worked under Sullivan in 1903, after serving as his assistant for 20 years.