This fonds consists primarily of the professional business records of barrister, solicitor and civil servant, E. Allison MacKay of Fredericton, New Brunswick. It consists of business correspondence, legal documents, receipts, memoranda, and statements of account. Much of his legal work related to property transactions, the settling of estates (probate), debts, bankruptcy, immigration, and civil suits. A Presbyterian, he accepted several legal cases involving the Presbyterian Church of Canada, notably, Ferguson et al v. McLean et al, a dispute arising in the congregation of St. James Presbyterian Church at Newcastle, N.B. over union with the United Church of Canada.

The fonds also includes correspondence, circulars, minutes of meeting, and notes relating to MacKay's work as secretary of the executive committee of the Children's Aid Society, chaired by W. J. West, that facilitated the placement of evacuated British children in the homes of York and Sunbury County residents during World War Two.

Also included are a few pieces of personal correspondence, as well as documents, correspondence and other material pertaining to his work with, or membership, in the Independent Order of Foresters, the Knights of Pythias, and St. Andrew's Presbyterian Church.

A series of six albums of 1,527 postcards collected by Ethel Anderson from 1905 to c.1911 and were donated by the executors of her estate as stipulated in her will and a series of 26 leather postcards.