Due to his loyalty to the Republican party during his four years in Congress, Isaac Parker stood a good chance of receiving an appointment to a government office from the President. In early March, 1875, President Grant forwarded Parker's nomination as chief justice of the Supreme Court of the Utah Territory. However, by this time, Parker had submitted a request for appointment as the judge of the federal district court for the Western District of Arkansas, in Fort Smith. On March 18, 1875, the President nominated Parker as judge for the Western District of Arkansas.
The federal court for the Western District of Arkansas was initially established in 1851, having jurisdiction over the western counties in Arkansas, and all of the Indian Territory (present-day Oklahoma). Until 1871, the court was based in Van Buren, Arkansas. In 1871, Judge Parker's predecessor, William Story was appointed to the bench. The tenure of Judge Story was marred by serious corruption, and in 1874, Judge Story resigned.
The new Judge arrived in Fort Smith on May 4, 1875, having traveled aboard the steamboat Ella Hughes. His family stayed behind in Missouri and joined him in Arkansas later. The judge held court for the first time on May 10, 1875. In the first term of court, eight men were found guilty of murder and qualified for a mandatory death sentence according to federal law. On September 3, 1875, six men were executed at once on the Fort Smith gallows; an indication that the once corrupt court was functioning once again.