Jack Stark (Wisconsin Legislative Reference Bureau) has published A History of the Wisconsin Inheritance Tax, 88 Marq. L. Rev. 947 (2005). Here is the Introduction:

Wisconsin’s inheritance tax, which was repealed in 1987, never generated a large portion of the state’s revenue; however, the potential and actual inheritance tax liabilities of some wealthy and influential persons created contention and political significance. Moreover, the nature of the tax–it was a tax on the transfer of property upon death–and certain attributes of the tax readily provoked ideological arguments. In fact, the inception of the tax, some of its modifications, and its discontinuation reflect important changes in Wisconsin’s political climate. Furthermore, the tax was frequently litigated. Many of the cases involved only marginally important issues, but some of them forced, or allowed, judges to deal with a few of the weighty issues that confronted legislators. For these reasons, the importance of the inheritance tax in Wisconsin’s political and legal history greatly outweighs the tax’s fiscal significance.