He served as a clerk in the law office of Hillard, Hyde & Dickinson until 1878 when he was admitted to the Suffolk County bar.

[1] On January 9, 1878, Allen married Lucy Rhodes of Lynn, Massachusetts.

[1] From 1884 to 1886 he was a member of the Massachusetts Republican state committee from the 1st Essex Senatorial District.

[2][4] As an attorney, Allen argued on behalf of the Plymouth Woolen Company of the constitutionality of a law allowing municipal officers to permit manufacturers "to ring bells and use whistles and gongs for the benefit of their workmen.

[2] In 1884 Allen organized the Massachusetts Temperance Home for Inebriates in Lynn.