Monrovia is located in the southwest corner of Section 12, Monroe Township, Morgan County, Indiana. State Road 39 enters the town north and south and State Road 42, as Main Street, is east and west. Their intersection is in Monrovia. The original name of Pleasant Grove was discarded since postal officials found another town in Indiana by that name. The town was platted on June 10th, 1834 with 45 lots. By 1853 at least 52 more had been added. In the early 1800's, this was a community of "Friends," also called "Quakers." The West Union Meetinghouse, organized in the 1820's, was built in 1832 and was the first church and the first school in the area.

Today there are approximately 600 citizens. The Monroe-Gregg School District and the Monroe-Gregg Volunteer Fire Department serve the area. Monrovia is incorporated and the Monrovia Police Department was established in 1998 with the first female Police Chief in the County. Local churches include the Monrovia Christian Church, Monrovia Methodist Church, Monrovia Nazarene Church and the West Union Meetinghouse.