Some family letters are in this series. Rowland wrote to Harriet Rowland, his mother, and Jennie and Mary Rowland, his sisters, while at school and during his tenure at Hopkins. The letters span 1865-1901. Correspondence of Henrietta Harrison Rowland, Henry Rowland's wife, and Harriette Rowland, their daughter, are included here. Most of the letters are incoming, with a few drafts of outgoing letters by Mrs. Rowland. There is a selection of Henry Rowland's letters written to Mrs. Rowland from the World's Columbian Exposition in 1893. Other of Mrs. Rowland's letters were received after Henry's death, and focus on various legal problems she encountered over royalties on Rowland's patents. There are also folders of invitations filed with Henrietta's correspondence.

There is some correspondence relating to honors and awards in the Personal Series Box 16. Correspondence regarding the Multiplex Telegraphic Company and the Cataract Construction Company are in Series 5 and 6.