In 1864, Union General Frederick Steele's failure in the Camden Expedition of March 23 – May 2, 1864 was largely due to Shelby's brilliant and determined harassment, in concert with other Confederate forces. Steele's men were forced to retreat to Little Rock by the destruction or capture of their supply trains at the Battle of Marks' Mills. Reassigned to Clarendon, Arkansas, Shelby succeeded in capturing a Union tinclad (lightly armored) gunboat, the . The gunboat was burned to prevent her recapture. Shelby then commanded a division during Price's Missouri Expedition. He distinguished himself at the battles of Little Blue River and Westport, and briefly captured many towns from their Union garrisons, including Potosi, Boonville, Waverly, Stockton, Lexington, and California, Missouri.