With Sturgis, the regiment marched across the Potomac into Virginia, but returned to Washington when Jackson's threat to the city subsided.

After a few days, on Monday morning, June 30, the 10th was detached from Sturgis' troops and ordered to relieve the 59th New York in the seven forts and three batteries it had been occupying.

[2] U. S. Army Engineers had designed Franklin to protect the city's receiving reservoir (as conveyed by the Aqueduct) as well as the river shoreline.

Although it was a crossbeam truss structure that resembled a long garden arbor or pergola, it retained the historical name associated with the site.

Located downriver and overlooking the aqueduct's distributing reservoir was Battery Cameron, mounting two 100-pounder Parrott guns.

Fort Pennsylvania, on the highest point of the northwest's defensive line,[8][note 1] protected this nerve center and was manned by three companies of the 10th, B, K, and L. The regiment's remaining company, D, was ordered to the defenses of the Rock Creek valley, due north of Georgetown and a half-mile east of Tennallytown.

[note 2] This fort, the largest of four works in the network, commanded the Milkhouse Ford Road across Rock Creek.

Controlling this ford protected the rear access to Fort Stevens, the headquarters for the northern defenses of the capital.

After a reception by local citizens, the regiment was dispersed to local armories until Friday morning the evening when it boarded the steamer, Bay State, and sailed from New York at 1:00 p.m.[11] The steamer arrived in Narragansett Bay on Saturday, August 30.