Born near Owensboro, Kentucky, McCreery graduated from Centre College, in Danville, Kentucky, in 1837. He studied law, passed the bar, and commenced practice in Frankfort, Kentucky. He then returned to Owensboro and engaged in literary pursuits.

He ran unsuccessfully for election in 1842 to the Twenty-eighth Congress, and again in 1844 to the Twenty-ninth Congress. He served as a presidential elector on the Democratic tickets in 1852, 1856, and 1860. He was finally elected as a Democrat to the United States Senate to fill the vacancy caused by the resignation of James Guthrie, and served from February 19, 1868 to March 3, 1871, when he was an unsuccessful candidate for reelection. He was again elected to the United States Senate in 1872 and served from March 4, 1873 to March 3, 1879, when he declined to be a candidate for reelection. He retired from public life and lived on his farm in Daviess County, Kentucky, and moved back to Owensboro, where he died and was intered in Elmwood Cemetery.