Petersburg quickly grew, due to an advantageous placement on the river, becoming the county seat in the 1830s and eventually drawing off the population of New Salem, which was abandoned in 1840.

[5] Many of the lush Victorian-era homes built by early wealthy inhabitants still stand on the bluffs of Petersburg.

The town itself takes great pride in these structures, which has even preserved some of the original cobblestone streets to complement the classical architecture.

There are also a growing number of bed and breakfast inns, many of which are located in restored Victorian homes.

Recent developments have also turned the town into a bedroom community for the state capital of Springfield, Illinois, which is 23 miles (37 km) to the southeast.

Petersburg is located in central Menard County and Illinois Route 97 passes through the city on Sixth Street, leading northwest 25 miles (40 km) to Havana and southeast 23 miles (37 km) to Springfield, the state capital.

The trees are mostly deciduous maples and oaks, and New Salem State Park is home to a sizable stand of old-growth forest.

The city and Menard County have since undertaken a campaign to buy and eliminate the low-income housing located in the most flood-prone areas, creating a small series of parks near the Sangamon River.

Petersburg is served by WCIA, WICS, WAND, WSEC, WRSP television stations.