Born in Granville, Ohio, Hillyer attended Denison University.
He read law to enter the bar in 1856 and was in private practice in Placer County, California from 1856 to 1861.
He was a lieutenant colonel in the United States Army during the American Civil War, from 1861 to 1865, and in the JAG Corps, Department of the Pacific from 1865 to 1866.
[1] On December 15, 1869, Hillyer was nominated by President Ulysses S. Grant to a seat on the United States District Court for the District of Nevada vacated by Judge Alexander W. Baldwin.
He received his commission the same day and served in that capacity until his death on May 10, 1882, in Carson City, Nevada.