The letters from the 1850s- 1860s are generally one page business letters dealing mainly with Ayer's mercantile business at Lincoln, Maine. The 1870s letters are likewise mainly one page business letters, but these deal with the lumber business that Ayer became involved in, in partnership  with Caleb Holyoke, David R. Stockwell, Timothy Fuller and Chandler Bruce. Ayer acted as agent for the company, which was called "Mattanawcook Mill Company," but, it is also seen as the "Holyoke & Ayer Company."

The Mattanawcook Mill Company was a set of gang saws at the lower mill that sawed hemlock boards and provided the spool stock for the large Clark Thread Company. It seems to have been associated with the Mattanawcook Dam Co. The incorporators were Caleb Holyoke, David R. Stockwell, Timothy Fuller, Chandler Bruce, and William R. Ayer. These men bought the set of gang saws of Timothy Fuller in 1869. Apparently the company was underway in 1871, with William R. Ayer as agent, and continued till Ayer's death in 1881. Nothing is known of it after this date. The Dam Co. Act was approved in February 1873.

While the ephemera are dated from 1807 to 1911, the bulk of it is from the 1860s to the 1870s. The ephemera for the 1860s is made up mainly of receipts, accounts, or invoices for various foodstuffs, such as pork, codfish, corn, flour, sugar, or farm tools, such as scythes, or household or personal goods, such as, curtains, shoes, soap, etc. Other receipts are for monies paid by Ayer on notes borrowed or loaned to him, or for goods or services he contracted for, or for taxes that he paid. Receipts are on both printed letterhead and in manuscript form and show an array of vendors from Bangor, Maine, down to Boston, Massachusetts. The ephemeral materials from the 1870s are made up mostly of items relating to the lumber business Ayer was involved with, sometimes seen as Stckton & Ayer Company. This group of materials is likewise comprised of manuscript and partially printed letterhead receipts, for all types of items pertaining to the hemlock lumber business.

William R. Ayer (1825-1881)

William R. Ayer was born about  1825 at Newfield, York County, Maine, and he attended the Charleston Academy. He moved to Lincoln, Maine in 1846. Ayer married Rebecca M. C. Burnham (1823-1860) and had a son by the name of Horatio S. Ayer (1854-1928), who married Mary Roxanna (1858-1945). William Ayer was appointed as a civil officer, elected selectman, and served as postmaster at Lincoln. He also appears to have represented Lincoln in the state legislature, serving as a Democrat. During Ayer's time, Lincoln was the largest town in Penobscot County.

In 1850, Ayer, newly married to Rebecca, is listed as a merchant at Lincoln, Maine. In 1860, he is again listed as a merchant with $ 2000 in real estate, and $ 800 in personal estate. He is listed with his wife Rebecca (aged 37), and two young children Ellen (9), and Horatio (5). By the time the 1870 Census is taken, Ayer is listed as keeping a variety store, with real estate of $ 4500 and a personal estate of $ 3000. His wife died earlier that year on May 10, 1870. His daughter Ellen, now age 19, and his son Horatio, now 15, are enumerated with him. Horatio is listed "at home," Ellen as "keeping house."

About a year after his wife Rebecca died, Ayer married a second time on 30 March 1871, to a woman by the name of Emily A. Morrison, of Bangor, Maine. When the 1880 Census was taken, William R. Ayer was listed as a trader. He is enumerated with his second wife Emily, who is five years older than he is. His son Horatio and daughter-in-law Mary are also listed with him. Horatio is now a store clerk, presumably his father's store. The family has two live in servants, male and female, 23 and 26 years of age respectively. Ayer's daughter Ellen married James H. McAvity and moved to St. John's, New Brunswick, Canada. There was another daughter, Mattie, who died in infancy.

The following year, on 1 June 1881, William R. Ayer died. His second wife Emily A. Ayer (born 1829) moved back to Bangor, Maine and lived until 13 December 1889. Ayer's son Horatio, lived until 1928. Ayer, both his wives, and his son, are all buried at the West Broadway Cemetery, in Lincoln, Maine.