Marthasville is a city in Warren County, Missouri, United States. The population was 837 at the 2000 census. The Katy Trail, a 225-mile long bike path, passes through Marthasville, and the original grave of Daniel Boone is located there. In 1845, Boone's remains were disinterred and moved to Kentucky for burial. Resentment in Missouri about the disinterment grew over the years, and a legend arose that Boone's remains never left Missouri. Because of the many wineries from here east to Defiance, Marthasville is considered to mark one end of the "Missouri Weinstrasse".
Marthasville is located at 38°37′50″N 91°3′32″W / 38.63056°N 91.05889°W / 38.63056; -91.05889 (38.630458, -91.058864). According to the United States Census Bureau, the city has a total area of 0.8 square miles (2.2 km²), all of it land.
As of the census of 2000, there were 837 people, 321 households, and 230 families residing in the city. The population density was 999.5 people per square mile (384.7/km²). There were 340 housing units at an average density of 406.0 per square mile (156.3/km²). The racial makeup of the city was 96.77% White, 1.08% African American, 0.48% Native American, 0.36% Asian, 0.36% from other races, and 0.96% from two or more races. Hispanic or Latino of any race were 0.36% of the population.