The Thomas W. Miller papers are exclusively focused on his term in the 64th Congress. They include copies of bills introduced by Miller and reports from the Committee on Claims and the Committee of Accounts, on which he served. They also include exchanges with constituents and state and national Republican Party officials, along with documents relating to Miller's interest in the threat posed by the war in Europe, the German submarine menace, and the United States' naval preparedness. The papers reflect some of the war anxieties in the Wilmington business community.

The papers also reflect the political influence of the DuPont Company. Among the pre-war controversies involving the company were charges that it had provided technical secrets on explosives manufacture to its German counterparts and its offer to build a nitrogen-fixing plant for the government while opposing the bill to establish such a plant under government ownership at Muscle Shoals, Alabama.

The papers also include a pamphlet on fraud in the 1916 election for Republican state delegates and literature reflecting the continuing Progressive-Machine split in the national Republican Party at the time.