in 2018, the Manassas Gap Railroad (part of Norfolk Southern) ran parallel to Interstate 66 towards Thoroughfare Gap
Source: Historic Prince William, I-66 west of Haymarket - #279
in 2018, the Manassas Gap Railroad (part of Norfolk Southern) ran parallel to Interstate 66 towards Thoroughfare Gap
Source: Historic Prince William, I-66 west of Haymarket - #279
During the Civil War, there was no railroad line running through the entire Shenandoah Valley. The Winchester and Potomac Railroad linked Harpers Ferry-Winchester, but there was a gap between Winchester-Strasburg. The Manassas Gap Railroad connected Front Royal-Mount Jackson, but there was no line south of there until reaching the Virginia Central at Staunton. No track connected the Virginia Central to the Virginia and Tenneesee Railroad west of the Blue Ridge.
The Confederates in the southern half of the Shenandoah Valley had to be supplied by local resources, or by carting supplies in wagons north from Lexington and Staunton. Union forces had to rely upon wagon trains to bring supplies south of Winchester, and Confederate partisans under John Singleton Mosby raided the supply line often enough to affect Union strategy. The Union considered using the Orange and Alexandria Railroad to carry supplies to Manassas and then the Manassas Gap Railroad to get across the Blue Ridge, but that supply line ran through the heart of Mosby's territory.
In September 1864, as part of the Union campaign to block Shenandoah Valley supplies from reaching the Army of Northern Virginia entrenched at Petersburg, General Philip Sheridan raided "up" the Shenandoah Valley to Staunton. Though Sheridan burned many barns and mills in the 1864 Valley Campaign, the Union Army did not destroy the Virginia Central Railroad at Staunton or cross the Blue Ridge and block the railroad at Gordonsville until 1865.
General Jubal Early's Confederate Army in the Shenandoah Valley was defeated at Cedar Creek in October, 1864,and then withdrew south to Staunton. The Union Army considered setting up a base in Front Royal to support an occupying force during the winter of 1864-65. The initial plan was to keep steady pressure on the Shenandoah Valley and the Piedmont east of the Blue Ridge, using the Manassas Gap Railroad to ship supplies and troops aross the mountains as needed.
However, John Singleton Mosby's partisan rangers were effective in attacking US Military Railroad shipments in Northern Virginia. General Sheridan could not ensure a steady source of hay for horses or supplies for troops. Even burning all houses within five miles of the Manassas Gap Railroad was not sufficient to make use of that railroad reliable, so the Union shifted military strategy and sent Sheridan and his cavalry to Petersburg. The Winchester and Potomac Railroad, which had been rebuilt for six miles to Halltown before the burning, was rebuilt almost all the way to Winchester in November, 1864 to support the occupation forces during the winter.1
during the Civil War, the railroad network in Northern Virginia connected Alexandria to Mt. Jackson, and the route to Richmond required going through Manassas
Source: Library of Congress, Map of eastern Virginia (1862)
1. Virgil Carrington Jones, Gray Ghosts and Rebel Raiders, EPM Publications, 1984, pp.295-302; Daniel C. McCallum, "United States Military Railroads Report," Government Printing Office, 1866, p.6, p.9, https://openlibrary.org/books/OL24992627M/Reports_of_Bvt._Brig._Gen._D._C._McCallum_Director_and_General_Manager_of_the_Military_Railroads_of_ (last checked April 11, 2020)
in 1861, there were gaps in Shenandoah Valely railroad connections between Winchester-Strasburg and Mount Jackson-Staunton
Source: Library of Congress, Map of the southern states, including rail roads (Harpers Weekly, 1861)