From the Iowa Legislature homepage:

In 1917, friends of Senator William B. Allison, citizens and school children of Iowa, and the state legislature raised this memorial. A pivotal figure in Iowa's Republican party, Allison (1829-1908) represented Iowa in Congress for 43 years. He was twice a candidate for the presidential nomination of his party and was a close associate of every United States president from Abraham Lincoln to Theodore Roosevelt. Evelyn B. Longman of New York designed the monument. A central plaque picturing Allison is flanked by symbols of "Knowledge," "Legislature," and "Financial Prosperity" on the left, and "Peace," "Humanity," and "Agricultural Prosperity" on the right. The topmost figure, symbolizes "The Republic."

Biography of Evely Lognman: Evelyn worked for a wholesale dry goods store for six years until earning enough money to study at the Art Institute of Chicago at the age of 20. She completed her course work in only two years, graduating with highest honors in 1900. Mentoring under New York City sculptor, Daniel Chester French, she later received important commissions and won major competitions.Susan was the first woman sculptor accepted as a full member of the National Academy of Design.Susan became one of Larado Taft's "white rabbit" assistants who worked on sculpture for the 1893 World's Exposition. The highlight of her involvement of the St. Louis World's Fair was Evelyn's “Victory” statue, which was placed on top of the Festival Hall. Initially not intended on the prestigious top of the dome, the officials admired the beautiful statue so much that they placed it there. Longman’s statue was noteworthy because it depicted “Victory” as a man, not as a traditional woman.Later in New York, she worked closely with the famous sculptor Daniel Chester French on many projects, including the Lincoln Memorial.