Background
McMillan was born in Brownsville, Pennsylvania in 1826.
lawyer politician United States senator
McMillan was born in Brownsville, Pennsylvania in 1826.
He attended the Western University of Pennsylvania in Pittsburgh, Pennsylvania and studied law under Edwin M. Stanton, graduating in 1846.
He served on the Minnesota District Court, the Minnesota Supreme Court and as United States. Senator from Minnesota. During the Dakota War of 1862 McMillan served as a Second Lieutenant in a militia unit known as the Stillwater Frontier Guards which was only briefly active. In 1864 he was appointed to the Minnesota Supreme Court as one of two new justices to replace the recently resigned Justices Charles Eugene Flandrau and Isaac Atwater.
In 1874 he was promoted to Chief Justice to replace Christopher G. Ripley who had also resigned.
In 1875 the Minnesota Legislature elected him to serve as United States. Senator. He served in the 44th, 45th, 46th, 47th, 48th, and 49th United States Congresses from March 4, 1875, to March 4, 1887.
McMillan did not stand for re-election in 1886 and returned to his law practice after the end of his term. He died in Saint Paul on October 3, 1897.
He is buried in Oakland Cemetery in Saint Paul, Minnesota.