He was first honored politically by being elected to the office of County Treasurer, in which capacity he served out one term. In 1875 at the age of 28, he was elected to the Legislature. He was re-elected in 1877, when he was appointed chairman of the House Committee on Rail Roads, and led the movement for the Commissioner Bill, of which he was the author, and which became a law. He made a very brilliant record and surprised his most sanguine friends, by his skill as a leader and strength as a debater. In 1881 he was nominated for the office of Lieutenant Governor in a manner that demonstrated the confidence bestowed in him by his party. This trust was further demonstrated by the handsome majority he received at the coming election. He was in stalled as Lieutenant Governor January 12, 1882. He was re-nominated and re-elected in 1883. He is the youngest man who has yet served in the presiding chair of the Senate. With his youth he displayed an ability to discharge his duties wisely, while his sense of honor enabled him to discharge them faithfully.
After his term of office expired, he continued the practice of law, and in 1888, moved his law office from Carroll to Council Bluffs. Thus Carroll lost one of the ablest attorneys in western Iowa. He resigned the office of Lieutenant Governor in 1885 and moved to Topeka Kansas to accept the position as Legal Counsel for the Central National Bank of Topeka.
In 1887 the Atchinson, Topeka & Santa Fe Railroad Company induced him to move to
Denver and act as its attorney and counsel in the State of Colorado, as it was then
building to Denver and making large extensions to its system in Colorado.
Mr. Manning was with the Santa Fe until April 1889, when he moved to Chicago to take
charge of the legal interests of a number of Illinois corporations under a fifteen-year
contract.
He at present resides at No. 3431 Michigan Avenue, Chicago, and still retains a lively
interest in the vigorous town of Manning, which bears his name.