Almost certainly from the collection of John Wilson Croker, these letters are probably those not used by Louis J. Jennings in writing Croker's Correspondence and Diaries (London: John Murray, 1884). They are almost exclusively from Murray to Croker. Many are addressed to Croker, and those that are not may be assumed, from their contents and presence in the collection, to be from Murray to Croker. They cover the years between 1809 and 1842. The core of the collection, 318 letters was sold by a London bookseller to Dr. Walter E. Peck in 1925. These were sold to Luther Brewer of Cedar Rapids sometime in 1928. Brewer later sold the collection to Special Collections at University of Iowa Libraries. One of the owners added some items because the collection now consists of 342 pieces. Some letters are missing, with an annotation that they were returned to Dr. Peck. In most such cases, the transcription is still in the collection. This collection is part of the Leigh Hunt Collection.

The letters are inlaid in folios, with front and back visible. The folios were assigned numbers, probably by Dr. Peck. They are not in chronological order, and most of them are undated, or marked only with the day of the week. Andrew J. Green, a student at Washington State College in the late twenties, wrote a Master's thesis on the letters, and several copies of this thesis are part of the collection. He also transcribed the letters and annotated the folios with the primary subjects of the letters. These transcriptions are part of the collection, as well. The numbering system created by Dr. Peck has been used to organize these letters, and Green's annotations have been retained and, in some cases, augmented.