In total, more than two centuries of payments on original agreements, court awards, and settlement acts represent more than 99.5 percent of the United States’ expenditures to secure title to the Louisiana Territory. It’s a thicket of payments so dense and deep that it would be impossible to venture through without a shortcut. The key to amassing the data presented here is forensic accounting reports, hundreds of them, compiled by a task force that operated out of the General Accounting Office, now the General Accountability Office, at the height of Indian claims litigation. It was charged with combing through old records to determine how much the United States had spent on past Indian treaties and agreements. The reports it issued provided the research into the fiscal history of U.S.-Indian relations that enabled the courts to say how much the Sac and Fox, or the Blackfeet, or the Sioux, or scores of other tribes had been paid for land cessions. The research was undertaken so painstakingly because it furnished the Department of Justice with the records of past payments, which were in turn used to protect federal coffers by adjusting final awards downward. It also amassed a long paper trail that, in conjunction with legal decisions, settlements, and other documents, makes it possible to assemble this $2.6 billion in transactions.