[7] In 1862, the city was the scene of the Palmyra Massacre, in which ten Confederate prisoners were killed in retaliation for the disappearance of a local Union man.

[9] Palmyra is in east-central Marion County, 13 miles (21 km) northwest of Hannibal, the largest city in the county, and 6 miles (10 km) west of the Mississippi River.

According to the U.S. Census Bureau, Palmyra has a total area of 3.10 square miles (8.03 km2), all land.

Daily Amtrak trains to downtown Chicago leave from nearby Quincy, Illinois.

Palmyra's school district serves a 200-square-mile area with 6,700 people; there are 1,150 students and 170 teachers and staff.

There are strong early childhood programs, a private parochial school and several day-care facilities.

29.3% of all households were made up of individuals, and 14.8% had someone living alone who was 65 years of age or older.

30.0% of all households were made up of individuals, and 16.1% had someone living alone who was 65 years of age or older.

About 5.5% of families and 8.1% of the population were below the poverty line, including 7.3% of those under the age of 18 and 10.5% of those 65 and older.