Its varied history includes the Mulhollen Station, through which mail traveled with the Butterfield Stage Line in 1858. Established in 1853, the Martin Hotel was visited by P. T. Barnum and Jesse James. Listed on the National Register of Historic Places in 1978, the Martin Hotel operates as a museum. The Morgan County Courthouse, established in Versailles, burned in 1887; however, the majority of the records were rescued, and the courthouse was soon rebuilt.
According to the 2000 U.S. Census, the county has a total area of 613.89 square miles (1,590.0 km2), of which 597.41 square miles (1,547.3 km2) (or 97.32%) is land and 16.48 square miles (42.7 km2) (or 2.68%) is water.
There were 7,850 households out of which 26.60% had children under the age of 18 living with them, 60.50% were married couples living together, 7.10% had a female householder with no husband present, and 29.30% were non-families. 25.10% of all households were made up of individuals and 11.90% had someone living alone who was 65 years of age or older. The average household size was 2.42 and the average family size was 2.88.
In the county the population was spread out with 23.80% under the age of 18, 6.20% from 18 to 24, 23.10% from 25 to 44, 27.30% from 45 to 64, and 19.60% who were 65 years of age or older. The median age was 43 years. For every 100 females there were 97.20 males. For every 100 females age 18 and over, there were 95.00 males.
The median income for a household in the county was $30,659, and the median income for a family was $35,908. Males had a median income of $26,579 versus $19,072 for females. The per capita income for the county was $15,950. About 12.10% of families and 16.20% of the population were below the poverty line, including 25.60% of those under age 18 and 9.70% of those age 65 or over.