After recovering from his illness, Gill returned to his law practice, and eventually return to public office. At the 1865 Union Republican State Convention, Gill was nominated by the party for Attorney General of Wisconsin on a ticket with fellow war veterans Lucius Fairchild for Governor and Thomas Allen for Secretary of State. Before taking his place on the ticket, Gill spoke out strenuously in opposition to the party platform offered by their own United States Senator, James Rood Doolittle. Doolittle's platform endorsed Andrew Johnson's reconstruction plans and opposed suffrage for African Americans. Gill did not prevail at the convention, as Doolittle's platform was adopted by the party. However, after the Republican victory in the 1865 election, the members of the new legislature quickly wrote a resolution demanding the resignation of Senator Doolittle, essentially vindicating Gill's criticisms. Gill was elected Attorney General in the 1865 general election and went on to re-election in 1867.