James Russell Soley, Professor U. S. Navy, Confederate Military History, a library of Confederate States Military History: Volume 7.1, The blockade and the cruisers
Clement Anselm Evans, Ed.

The third measure adopted by the Department, on its own responsibility, without waiting for the action of Congress, was to contract with private parties for the construction of small, heavily armed screw-gunboats. Twenty-three of these were built, of which the Unadilla and Pinola may be regarded as types. They were of five hundred and seven tons each, and mounted from four to seven guns. Some of them, within four months from the date of contract, were afloat, armed, and manned, and took part in the battle of Port Royal. From their rapid construction, they were commonly known as the ‘ninety-day gunboats.’ Nine of them were in Farragut's fleet at the passage of the forts below New Orleans. They were an important addition to the navy, and were actively employed both in fighting and blockading during the whole war.

For service in the rivers and in narrow sounds and channels, still another class of vessels was needed. To meet this want, a fourth measure was adopted, by building twelve paddle-wheel steamers, three or four hundred tons larger than the gunboats, but still small vessels, and of very light draft. To avoid the necessity of turning, they were provided with a double bow, and a rudder at each end. These were the famous ‘double-enders.’ The first twelve were the so-called Octorara class. Twenty-seven larger vessels of the same type were afterwards built, composing the Sassacus class. The Wateree, a vessel of the same size and general design, was built of iron. Finally the Mohongo class, also of iron, consisted of seven double-enders of still larger size, and carrying a heavier armament. The Ashuelot¹ and Monocacy still represent this class in the service

The fifth and last measure for the increase of the naval