Who was hired by Grant's Secretary of the Treasury to collect unpaid taxes, retaining half of the profits collected?

The correct answer is John D. Sanborn. He was contracted by the Secretary of the Treasury under Ulysses S. Grant's administration to assist in collecting unpaid taxes. Sanborn operated under a unique arrangement whereby he was permitted to keep a significant portion of the revenue he collected—specifically, half of the profits. This practice was designed to motivate collectors to pursue delinquencies more aggressively, as they had a financial incentive to ensure the recovery of outstanding taxes.

This context reflects the challenges faced by the federal government in collecting taxes during the post-Civil War period, a time characterized by financial instability and the need for effective revenue collection. Such arrangements, while beneficial in some aspects, also contributed to criticism regarding corruption and the fairness of tax collection practices during that era. This issue was emblematic of the broader economic and political difficulties of the time.