Cusack emigrated with his family from Ireland to New York City in 1861 when he was a young boy. Shortly after the move, his parents died, leaving him and his younger brother orphaned. Cusack was raised by relatives in Chicago, where he received his education and learned how to paint, a skill that ultimately made him a very wealthy man. At the age of 17, Cusack established his own sign painting business, the Thomas Cusack Company, in Chicago, Illinois, making him one of the pioneers in the field of outdoor advertising. The business soon grew to be very profitable, leasing over 100,000 billboards and advertising spaces and turning Cusack into a prosperous and influential Chicagoan.[citation needed]
In addition to business savvy, Cusack had a strong sense of civic duty. In 1890, Mayor of Chicago Hempstead Washburne appointed the "billboard baron" to a seat on the city's school board. Cusack's fervent support of public education drew the attention of progressive Illinois Governor John P. Altgeld, who invited Cusack to serve on his general staff. In 1898, Cusack was elected to his first and only term in the United States Congress from the 4th District of Illinois. After his term, Cusack decided to return his attention primarily to his outdoor advertising business, which had grown considerably in size to more than one hundred offices with an annual revenue of over $20 million. Cusack was known for his fair labor practices and amicable relationships with his employees, and was most proud of the fact that, in a city known for labor strikes, his workers never walked off the job. In his day as a sign painter, Cusack remembered getting $8 a week in wages. By the time he sold his business to a New York banking syndicate in 1924, he was paying his workers $10 to $15 a day.[citation needed]
At the pinnacle of his success in business, Cusack bought the entire unincorporated town of Cascade, Colorado, at the Ute Pass in the Rocky Mountains. He hired architects and contractors to build a plush mansion nestled in the Ute Pass, which he named "Marigreen Pines" after his wife, Mary Green. Having lived through the Great Chicago Fire and experienced so many early losses in his life, Cusack built Marigreen Pines out of brick, marble and concrete to safeguard his family from harm. Marigreen Pines became a much loved mountain home for Cusack and his family, where he routinely and graciously hosted many friends and relatives, engaging them in lively conversation and debate.[citation needed]