The Big Sandy Expedition was an early campaign in Kentucky that began in mid-September 1861 when Brig. Gen. William "Bull" Nelson received orders to organize a new brigade at Maysville, Kentucky and conduct an expedition into the Big Sandy Valley region of Eastern Kentucky and stop the build-up of Rebel forces under Col. John S. Williams. This was done in three phases. From September 21 to October 20, 1861, Nelson assembled a brigade of 5,500 Union volunteers from Ohio and Kentucky. On October 23, the southern prong secured Hazel Green and the northern prong West Liberty. The two prongs were consolidated at Saylersville (Licking Station) and they began the final phase on October 31. This led to the Battle of Ivy Mountain on November 8 and the withdrawal of Rebel forces from Pikeville (Piketon) on November 9, 1861.