After Senator Kinsley S. Bingham died in 1861, Howard was elected to fill the vacancy, taking office in January 1862.

[2] He was city attorney of Detroit in 1834 and joined the unofficial militia Governor Stevens T. Mason formed for the Toledo War in 1835–1836.

[4] Howard became identified with the anti-slavery wing of the Whig Party, and campaigned for presidential nominees Henry Clay (1844), Zachary Taylor (1848), and Winfield Scott (1852).

[2] Howard was widely read in the classics, history, law, and literature, and published the memoirs of the Empress Joséphine after translating them from the original French.

[4] As a Senator, he was the chief sponsor of the False Claims Act, the "Lincoln Law", which permitted whistleblowers to file qui tam lawsuits against government contractors for fraud, with the incentive of receiving a monetary reward based on the recovery made by the federal government.

[8]Howard is credited with working closely with Abraham Lincoln in drafting and passing the Thirteenth Amendment, which abolished slavery.

[5] During the debate over the first clause of the Fourteenth Amendment, Howard argued for including the phrase "and subject to the jurisdiction thereof:" ...[E]very person born within the limits of the United States, and subject to their jurisdiction, is by virtue of natural law and national law a citizen of the United States.

[9]Howard clarified his statement during the original congressional debate over the amendment describing the clause as having the same content, despite different wording, as the earlier Civil Rights Act of 1866, which reads: “all persons born in the United States and not subject to any foreign power, excluding Indians not taxed, are hereby declared to be citizens of the United States”.

He said of the exclusion of Native Americans who maintain their tribal ties: I am not yet prepared to pass a sweeping act of naturalization by which all the Indian savages, wild or tame, belonging to a tribal relation, are to become my fellow-citizens and go to the polls and vote with me.According to historian Glenn W. LaFantasie of Western Kentucky University, "A good number of his fellow senators supported his view of the citizenship clause.

[2] According to published accounts, he overexerted himself while helping take down a tree on the property line between his house and his neighbor's, and burst a blood vessel in his brain, which caused his death two days later.

[2] They were the parents of seven children: Edward Wellington, who died at age 3; Catherine Amelia, died at age 5; Mary Elizabeth, the wife of Dr. Joseph S. Hildreth; Colonel Jacob Merritt Jr., a Union Army veteran and businessman in Litchfield, Minnesota; Hamilton Gay, a lawyer in San Francisco; Charles Millington, a mining engineer in Salt Lake City; and Jennie, the wife of Samuel Brady, a grandson of Hugh Brady.