At the outbreak of the Mexican–American War in 1846, Temple was residing at St. Louis, where he enlisted with the 2nd Illinois Volunteer Infantry Regiment under Colonel William Henry Bissell.

He marched with the army of General John E. Wool through Texas and Mexico, participating in the Battle of Buena Vista, and returned to Wisconsin in 1847.

[3] A few months after his arrival at Manitowoc, the federal government approved an appropriation for improving the harbor, and Clark gained significant patronage through awarding the contracts to complete the work.

[5] Clark was also active in the Democratic Party and, in 1856, was elected to the Wisconsin State Senate from the 19th district, which the previous year had been redistricted to contain Calumet and Manitowoc counties.

Possibly the most noteworthy anecdote of his Senate term was that he was involved in a physical altercation with Madison Patriot publisher Stephen Decatur Carpenter on the grounds of the State Capitol.

Cobb and Governor Alexander Randall appointed Clark to serve as Major General for the 8th Division of the Wisconsin Militia, which comprised Manitowoc, Calumet, Brown, and Kewaunee counties.

Captain Clark, however, left the regiment in early April 1862, as he was appointed adjutant on the staff of his brother-in-law Brigadier General Joseph B. Plummer in the Army of the Mississippi.

[9] Clark returned to service in January 1863, and was assigned as an adjutant to General Richard W. Johnson in the Army of the Cumberland, but had to resign due to disability in July 1863.

[2] After the war, Clark resided for a time at New York City and was active in the Military Order of the Loyal Legion of the United States.

[10] Though Clark had always been a Democrat, he was a supporter of James A. Garfield in the 1880 United States presidential election, due to their time together on the staff of General Rosecrans.

After Garfield was elected president, he appointed Clark to a clerkship position in the United States Department of Agriculture, where he remained until his death in 1893.