He began his career in journalism while still a student at Bates College and, by the end of his life, was a leading press figure in the state.

In addition to running its largest morning and afternoon papers, he was a longtime trustee of both Bates College and the Androscoggin County Savings Bank, serving as the latter institution's president from 1931 to 1939.

[2][3][4] In 1889, his mother, Annie Hill Costello (1842–1927) remarried William S. Wells, a prominent York County lumberman who later served in the Maine House of Representatives.

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.

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][10] On June 15, 1952, in recognition of his achievements, including more than 30 years of service on Bates College's board of trustees, Costello was awarded an honorary Doctor of Laws degree by university president Charles Phillips.

[7] Other recipients honored at the ceremony were New Jersey Governor Alfred E. Driscoll, financier Frank Altschul, filmmaker Louis de Rochemont, and clergyman Daniel A.

Following services at the Bates College chapel, he was buried in Riverside Cemetery, alongside his wife, who preceded him in death two years earlier.

[31] The Costello family home at 45 Campus Avenue was purchased by Bates College and provided office and student organization space for a number of years before being torn down in 2014.