A believer in the New Church (Swedenborgianism), Clapp ultimately turned his focus in this field to New Church-related works.

It was one of the oldest-operating pharmaceutical manufacturers in the United States by the time it was acquired by Medique in 2008.

[1][3][6] This firm published a series of volumes titled "The American Library of Useful Knowledge", as well as the annual "Boston Directory".

[2][7] Initially, its inventory was limited, however as homeopathy grew more popular in New England so too did the pharmacy.

[12] Clapp served in both chambers of the (then-bicameral) Boston City Council.

He first served as a member of the Common Council from the city's sixth ward from 1845 through 1846.

[1][3] During the years in between his tenures in the Boston City Council's chambers, Clapp served a term as a member of the Massachusetts House of Representatives in 1854.

[1][17] He was also appointed by the Common Council in 1859 to serve as the city's assistant assessor for books and publishing.

[18] In 1862, President Abraham Lincoln appointed Clapp as the collector of Internal Revenue for the fourth district of Massachusetts.

[1][2][8] Clapp played a significant role in the founding of the Boston Female Medical College.

He served as president of the Washingtonian Home,[1] a role he held at the time of his death.

[1] In some obituaries for Clapp (published in newspapers such as the Brooklyn Eagle), he was described as having been "prominent in many political, social and business reforms.