[1] During the American Civil War, Dyer served as a private in Captain Hardin’s company, Pike County Regiment, Missouri Home Guard, and as lieutenant colonel and colonel in the 49th Missouri Infantry Regiment.

[2] Dyer was elected as a Republican from Missouri's 9th congressional district to the United States House of Representatives of the 41st United States Congress, serving from March 4, 1869 to March 3, 1871.

[2] Following his departure from Congress, Dyer resumed private practice in St. Louis, Missouri from 1871 to 1902.

[2] Dyer was nominated by President Theodore Roosevelt on February 27, 1907, to a seat on the United States District Court for the Eastern District of Missouri vacated by Judge Gustavus A.

[1] He was confirmed by the United States Senate on March 1, 1907, and received his commission the same day.