Petersburg is a city in Monroe County in the U.S. state of Michigan. The population was 1,167 at the 2000 census. Petersburg is named after Richard Peters, who sold the land necessary to found the town in 1836. It was originally called Summerfield and Peters was its first postmaster, but it was later named Petersburgh in honor of Peters and was eventually shortened to Petersburg. Petersburg is served by Summerfield Schools.
According to the United States Census Bureau, the city has a total area of 0.5 square miles (1.2 km²), all land.
As of the census of 2000, there were 1,157 people, 423 households, and 307 families residing in the city. The population density was 2,497.8 per square mile (971.1/km²). There were 442 housing units at an average density of 954.2 per square mile (371.0/km²). The racial makeup of the city was 96.80% White, 0.35% African American, 0.43% Native American, 0.09% Asian, 0.35% from other races, and 1.99% from two or more races. Hispanic or Latino of any race were 1.12% of the population.