[1] While on the federal bench, Dillon wrote Municipal Corporations (1872), one of the earliest systematic studies of the subject.

[citation needed] On February 17, 1876, during the Whiskey Ring graft prosecutions, Justice Dillon ruled Ulysses S. Grant's deposition for Orville E. Babcock was admissible in court.

[1] A memorial fountain to Dillon was erected in downtown Davenport in 1918, carved of Indiana limestone in Romanesque style, by sculptor Harry Liva.

[citation needed] In 1853, Dillon married Anna Margery Price (born June 19, 1835).

Anna and their daughter, Mrs. Annie Dillon Oliver, died in the sinking of the French ocean liner La Bourgogne in July 1898.

The theory of state preeminence over local governments was expressed as Dillon's Rule in an 1868 case: "Municipal corporations owe their origin to, and derive their powers and rights wholly from, the legislature.

"[6] The Supreme Court of the United States cited Municipal Corporations and fully adopted Dillon's emphasis on state power over municipalities in Hunter v. Pittsburgh,[7] which upheld the power of Pennsylvania to consolidate the city of Allegheny into the city of Pittsburgh, despite the objections of a majority of Allegheny's residents.

However, the Court did not prevent states from passing legislation or amending their constitutions to explicitly allow home rule.