Born in Buxton, Maine, he worked various jobs before becoming an agent of the Pennsylvania Railroad Company in 1860.

After the war, Amos married Johanna Currier, and moved to Buxton to begin farming.

According to an 1888 profile in the Daily True American and a biography in History of Omaha from the Pioneer Days to the Present Time (1889), Kimball lived with his parents until the age of seventeen, at which point he studied academically until the age of twenty-one, and taught school during his summer vacations.

[3][1] On the contrary, his biographies in History of the City of Omaha, Nebraska and South Omaha (1894) and in Omaha: The Gate City and Douglas County Nebraska (1917) claim that he had planned to attend college at the age of sixteen, but was ill for a period of two years, preventing him from doing so, and makes no mention of him teaching school during his summers, instead claiming that he worked at a jewelry firm based in Saco, Maine, (though most of his work at the firm was done in Biddeford, Maine).

[3] In 1859, he wrote a series of articles about the Western United States[1] and the Pennsylvania Railroad Company.

[7] Thomas A. Scott, an associate of Kimball, was elected as the president of the Union Pacific Railroad in March 1871.

However, after Union Pacific acted to block the Milwaukee and Rock Island railroads from entering the city, Ernest Stuht filed suit against the city of Omaha, many of its officials, the Union Depot Company, and Kimball, seeking to block the bonds.

[14] Frances Kimball married George Ward Holdrege, another prominent railroad executive.