Created on May 3, 1850 from part of Columbia County and named for Madame Montour, a woman of Indian and French descent who was prominent in the Indian affairs. Danville, the county seat, was laid out in 1792 and incorporated as a borough on February 27, 1849. It had been the county seat of Columbia County from 1813 to 1846.

     The Mahoning Creek area was settled beginning in 1769. Danville is named for Daniel Montgomery, son of early settler General William Montgomery. It had been Columbia County’s seat until 1845, but when Bloomsburg usurped Columbia County Danville wanted a new county so it could once more be a county seat. Newspaper activist Valentine Best went to the legislature and pushed the creation through. Danville became a highway, canal, and then rail link on the North Branch route from Sunbury to Wilkes-Barre. Danville’s Big Mill, eventually owned by Bethlehem Steel, made iron and steel from 1838 to 1938, Rails were a specialty—the first T-rails made in the United States were made here. In 1873 a national financial panic eclipsed the mill’s future, it lost out in competition with Bessemer process and Lake Superior ore, and in 1896 it experienced a major explosion. But iron and steel specialties production continued until the end of World War II. Silk and shirt-making factories were productive from the early 1900s. Half of the county’s area is farmed.