The affiliates subseries (56.70 linear feet), arranged chronologically by year then alphabetically by state, contains mailings from the national office to affiliates, board minutes of affiliates, general correspondence, and affiliate publications. In states with several chapters, material is filed by city or chapter name within each state. In the early years many states had civil liberties committees but not full fledged affiliates. These files are labeled "committee."

Between 1947 and 1960 the number of national affiliates increased, growing in number from 15 to over 25. Affiliates in Southern California, Northern California, New York, Pennsylvania and Ohio make up the largest percentage of the holdings for these earlier years. Some individuals in these affiliates have their own runs of correspondence, including A.L. Wirin (Southern California), and William Sanborn (regional director of Ohio, Indiana and Michigan). Various state committee minutes are present as well as updates on cases that were being tried by the state affiliates. There are gaps in the board minutes for all affiliates from 1970 to 1990. From the mid-1970s, the number of board minutes decreases. Affiliate publications are found sporadically, as are news releases, and pamphlets published by either the affiliate or the national office.