Born in Richmond, Kentucky, McCreary graduated from Centre College in Danville, Kentucky in 1857, and from the law department of Cumberland University at Lebanon, Tennessee in 1859. He was admitted to the bar in 1859 and commenced practice in Richmond.

McCreary entered the Confederate States Army in 1862 and attained the rank of lieutenant colonel before the close of the American Civil War. He then became a member of the Kentucky House of Representatives from 1869 to 1875, serving as speaker from 1871 to 1875. He became the Governor of Kentucky, holding that office from 1875 to 1879.

McCreary was appointed by President Benjamin Harrison to be a delegate to the International Monetary Conference held in Brussels, Belgium, in 1892. He was subsequently elected as a Democrat to the U.S. House of Representatives, serving from March 4, 1885 until March 3, 1897. He ran unsuccessfully for renomination in 1896, after which he resumed the practice of law. He was later elected to the United States Senate and served from March 4, 1903 to March 3, 1909, when he ran unsuccessfully for reelection in 1908.

McCreary was again elected Governor of Kentucky, serving this time from 1912 to 1916. He ran again for election to the United States Senate in 1914, but was defeated, and again resumed the practice of law. He died in Richmond and was interred in Richmond Cemetery.