Miner's final and most influential anti-slavery effort occurred in January 1829. In preparation for his proposal, he visited prisons and auctions to discuss the issue of slavery with slaves and jail keepers.17 He was especially disturbed to learn that free men were kidnapped and sold as slaves or imprisoned for minor debts. All black people in the District of Columbia were assumed to be slaves unless they could provide proof for their freedom, so free men were often mistaken for runaways, arrested, and sold into slavery.16 In Miner's final speech, he recalled the cruelty he witnessed, exposing the House to the brutal reality of the slave trade.17 Miner and his supporters also cited Article I, Section 8, which justified Congress's power over the District of Columbia.18 At the end of the speech, he offered a series of resolutions that asked the House to investigate the injustices of the slave trade (particularly the arrests of free men, the District's prison systems, and the splitting apart of slave families16) and consider the gradual abolition plan. A large majority voted to inquire into Miner's resolutions.19