Petersburg

Abstract

The Petersburg Battlefield is divided between two Physiographic Provinces, the Piedmont and the Coastal Plain. Union General Ulysses Grant conducted most of his Overland Campaign across the Piedmont of Virginia before crossing the Fall Zone and directing a disastrous assault on Lee and the Army of Northern Virginia at Cold Harbor. For his next attempt to take Richmond, Grant decided to strike back towards the Piedmont, severing the Confederate rail lines into Petersburg. After initial assaults on the Confederate earthworks around the city failed, a nearly year-long siege witnessed the Union and Confederate entrenchments extend to the west from the sediments of the Coastal Plain to the hard rocks of the Piedmont. During this siege Grant would employ many of the engineering tactics he had used a year earlier during his siege of Vicksburg: For example, a massive canal was dug to bypass Confederate artillery positions along the James River and multiple tunnels were constructed in the Coastal Plain sediments to detonate a mine under a key position on the Confederate lines. The variation in soil type, regolith thickness, bedrock geology, and geomorphology between the Coastal Plain and Piedmont influenced all of these operations, often dictating the kinds of tactics that were used and the types of earthworks that were constructed.