This eight-volume collection of letters covers the period 1877-1890, and is probably the most important set of letter books in this period. Its importance is derived from the following: 1. the letters were written from the company's main office, 2. the company's policy-makers--Uri Balcom, D. R. Holt, George H. Holt, and W. A. Holt-wrote most of the letters, 3. over-all decisions, plans, motives, and problems of the company are more clearly revealed in this set of letters than in any other.

While compassing many of the routine subjects covered in the Oconto Letter Books, the Chicago volumes deal with more significant matters:

• Instructions to Oconto on land purchases and sales
• Periodic reports of the condition of the lumber market
• Reports on the well-being or financial straits of the company
• Difficulties involved in shipping on the Great Lakes
• Decisions respecting lumber quality and prices.
• Debits and credits charged to the Oconto branch
• Monthly records of lumber sales
• Seasonal records of shipments
• Information relating to dissolution of Holt and Balcom
• Personal data on the health and travels of Balcom and D. R. Holt

It seems certain that the proportion of useful historical data to useless data is greater in the Chicago Letter Books than in any other.

Like the Oconto volumes, those from Chicago are about one-tenth illegible. Indexing is more complete in the Chicago volumes, but it is by no means complete or foolproof. Nevertheless, the index frequently prove useful in tracing relations with a particular company over a period of time.