During his time in that role, in 1859, he came into conflict with the city council which was attempting to take more direct oversight of the school board and its affairs and finances.

As the 1860 presidential election began to shape up as a contest between Abraham Lincoln and John C. Breckinridge, Gill ultimately chose to align with the Republicans.

His committee was approved by the senate and he was named chairman—one of the earliest war preparation measures taken by a Union state.

A special session of the legislature was then held to further war preparations and Gill was again made chairman of the select committee for that purpose.

[1] After the special session, upon hearing that his native Watertown had not provided a significant quantity of volunteers for the war effort, Gill took up a recruitment commission.

As he addressed the gathered crowd to ask for volunteers, one person criticized Senator Gill for urging others to enlist when he was safe on a recruiting commission.

[1] Colonel Gill led his regiment through several battles of the Vicksburg campaign and earned the recognition of his colleagues.

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.

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.

[1] After leaving office in January 1870, he purchased a farm in Blooming Grove, Wisconsin, and moved his law practice to Madison.

Under President Grant, Gill was appointed attorney for the U.S. government in the negotiations over the Fox and Wisconsin Rivers improvements.