 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.