There, he served as chairman of the United States House Committee on Coinage, Weights, and Measures from 1863 to 1867, during which time the Metric Act of 1866,[3] which he drafted, was passed.

Afterward, he was a commissioner from the United States to negotiate postal conventions with Great Britain, France, Belgium, the Netherlands, Germany, Switzerland and Italy in 1867.

[5] In 1877 Kasson was appointed Envoy Extraordinary and Minister Plenipotentiary to Austria-Hungary by President Rutherford B. Hayes, a position he held until early 1881.

[6] In 1880 he ran once again for Congress, again winning the Republican nomination and general election to represent Iowa's 7th congressional district in the U.S. House.

His final period in Congress ended in 1884, when he was appointed Envoy and Head of the U.S. Legation at Berlin, Germany, by President Chester A. Arthur.