The Anderson-Nimicks letters are based on typed transcripts and (some) photocopies of 24 letters written by members of the related Anderson, Nimicks, Riddle, and Cochrane families to their kinsmen and -women in Aghadowey parish, County Derry, in 1832-1879. Most of the letters were written by immigrant brothers John, Joseph, David, and Robert Anderson from northwestern Pennsylvania, northeastern Ohio, and near Valparaiso, Indiana, and by elderly immigrant Samuel Nimicks from southern Illinois.
Per Miller, 'these letters illustrate:
- Transatlantic voyage in 1832 from Derry to Quebec; cholera epidemic of 1832 in Quebec.
- Chain migration and mutual assistance, resulting in dense (although sometimes fractious) networks of kin and former neighbors among Irish immigrant farmers in America.
- Detailed economic and social information, especially concerning immigrants' labor to acquire capital to rent, then purchase farms, and on farming, crops, livestock, prices, etc., in the Old Northwest, 1830s-1850s.
- Transatlantic Protestant (especially Presbyterian) evangelicalism; exchange of religious information and newspapers between Ulster and America; the great transatlantic religious revivals in the US and in Ulster, 1857-1860. Evangelical and apocalyptic attitudes among Ulster immigrants to US slavery, Southern secession, and Civil War.
- Special economic and psychological problems of immigrants who leave Ireland and America at advanced ages, and lose the support systems they formerly enjoyed.'
The series also includes: Kerby A. Miller's correspondence with researchers in Ohio and Pennsylvania, who supplied detailed information about the Anderson brothers' families and farms; research notes by Miller and his colleague, Bruce D. Boling, mostly from 19th-century Irish primary sources; and photocopied pages from histories of Derry shipping and Trumbull County, Ohio.