Newspapers

In 1898, Lewiston publisher George W. Wood purchased the five-year old Lewiston Daily Sun, merging it with his weekly Maine Statesman, and hired Costello as the paper's business manager. Thanks largely to the arrival of Rural Free Delivery in the region, which allowed for wider distribution within the Lewiston-Auburn city and town area, circulation increased from around 2,000 copies per day to 8,000 over the following two decades.^[10] In 1926, Wood acquired the Lewiston Evening Journal and promoted Costello to treasurer and general manager of the papers' publishing company.^[1] Costello served in this position until Wood's death in 1945, when he took over as owner and president.^[11] By this time, the Sun and Journal were the fourth and fifth most-read dailies in the state with circulations of 27,480 and 14,088, respectively.^[12]

Costello was generally conservative in his management style.^[13] He took interest in new technological developments, investing in a trained photography department in the 1930s, but strongly resisted the growth of non-print media, going as far as firing his general manager, Frank S. Hoy, when Hoy purchased the license for radio station WLAM without permission.^[14][15] Though the Sun grew during an era of political domination by the Maine Republican Party and historically embraced an "independent Republican" label, Costello stressed the importance of journalistic objectivity to those who worked under him.^[16][13] His papers gained a reputation for being socially progressive but not so much as to alienate readers averse to change.^[10][13] Writing under the headline "A Leaf Out of My Notebook," he shared with Sun readers reports of his and Sadie's cross-country travels.^[1] All the while, he remained devoted to his home state, with editorials focused on portraying local communities in a positive light.^[13] During his tenure, he served for a time as president of the Maine Daily Newspaper Publishers Association and of the Maine Members of the Associated Press.^[17][18][19]

Banking

Costello was named a trustee of Androscoggin County Savings Bank in 1916 and remained on the board until 1956.^[1] Androscoggin was the largest savings bank by assets held centered in Lewiston and one of the largest in the state.^[20] In 1931, Costello was elected president of the bank when incumbent William J. Crawshaw resigned due to ill health.^[21][22] He served in this position for eight years, seeing it through the Great Depression, including its accepting of Emergency Banking Act aid in 1933.^[1][23]

Civic life

Costello was a United Baptist, a designation common among Maine members of the Northern Baptist Convention into the twentieth century. He was a founding member of the Lewiston United Baptist Church. In the early 1920s, he served on the building committee for that congregation's now-demolished English Gothic home at the corner of Bates and Main streets, where Sadie taught religious school for many years.^[1][24] In 1932, he was named second vice president of the Maine United Baptist Convention; that year, convention delegates passed resolutions praising the United States' involvement in the World Disarmament Conference and opposing repeal of the Eighteenth Amendment to the United States Constitution.^[25]

He was also a Freemason, having served as a past master of Rabboni Lodge No. 150 and as a member of the Knights Templar fraternal order.^[1][10]