It was in Carroll County:

"Colonel Guitar, having returned to Jefferson City from Moore' s Mill on account of serious illness, immediately entered upon preparations for the pursuit of Porter, and on Friday, the 8th, landed from a steamer at Glasgow a considerable force. Continuing the pursuit, he overtook Porter at 9 o'clock on Monday night, at Compton's Ferry on Grand Eiver in Carroll County. A portion of Porter's men had crossed before his arrival, but a large number, with all their baggage, horses, wagons, etc, were yet to cross. Guitar ordered his troops, portions of his own regiment and portions of "Merrill's Horse" under Major C. B. Hunt, to charge, which they did, at the same time opening upon the demoralized and fleeing guerillas with two pieces of artillery. The effect was terrible. Many, in their eagerness to escape, threw away their guns and plunged on their horses into the river, but many of the horses became unmanageable and returned to the shore from whence they started. Some were drowned. A large number of prisoners, all their baggage, together with a great number of horses, mules, guns and wagons, were captured."

Switzler's illustrated history of Missouri, from 1541 to 1881
https://archive.org/details/cu31924087027516/page/414/mode/2up?q=ferry