In the nineteenth century, Izard County served as a gateway to settlement across northern Arkansas and was the parent county of seven other counties. Later, Izard County's virgin yellow pine forests provided lumber to other parts of the state.
According to some historians, John Lafferty, a native of Ireland, traveled up the White River in 1802 to what became known as Lafferty Creek. He built a log cabin and attempted to claim 640 acres following the Louisiana Purchase of 1803, but his claim was denied because he had not lived on the land for ten years. In spite of this setback, Lafferty and his family established the county's first settlement at Lafferty Creek in 1810.
In 1825, the territorial government split off part of Independence County, naming the new county for Governor George Izard. Adding Osage (1827) and Cherokee (1828) lands, Izard County covered most of north-central Arkansas. In 1833, western Izard County was divided into Van Buren, Carroll, and Johnson counties. Later, sections of Izard County were split off to become Marion (1836), Fulton (1842), and parts of Baxter (1873) and Stone (1873) counties.
Izard's first county seat and post office (then called Liberty, now Norfork in Baxter County) were established at the mouth of the North Fork River at Jacob Wolf's trading post. Sheriff John Adams and Clerk John Houston (brother of Sam Houston) were the first elected officials. The county seat was moved to Athens in 1830 and to Mount Olive in 1836. Mill Creek (later renamed Melbourne) became the county seat in 1875. Courthouses there burned in 1889 and 1937. From 1938 to 1940, the Civilian Conservation Corps (CCC) from Camp Sage (near Sage) built the current courthouse. It is the only courthouse in the country partly heated by a wood-burning furnace.