A unique collection of almost 5000 books, most of which were published in the seventeenth and eighteenth centuries, was presented to the Wisconsin Historical Library in 1867. It is known as the "Tank Collection." Because it formerly was the library of a Dutch clergyman living about a century and a half ago and because its emphasis is on Dutch Protestantism, information on it should prove of particular interest to ministers of the Reformed faith. Furthermore, lay scholars who are concerned with the Reformation, or the history of the Netherlands, or Dutch literature and linguistics should find much of value here. The college professor who is working in these areas or is advising students who are doing advanced research in these fields cannot afford to be unacquainted with the offerings of this collection. Although rich in information, the existence of this vast array of books is little known. The purpose of this article is to describe the background and contents of the collection in the hope that more scholars may become acquainted with it. Undoubtedly no periodical reaches a larger number of persons interested in Dutch Protestantism and the heritage of the Netherlands than The Reformed Review.