On July 7th, 1862, pursuant to orders from General John Pope, who desired to concentrate his new army (Army of Virginia) along the upper reaches of the Rappahannock River, General Franz Sigel marched his 1st Corps (including the 55th Ohio) out of Middletown toward Sperryville, Virginia (going via Front Royal, Luray and Thornton's Gap). William Keesy of Company I relates the story of that march:"Of all the trying ordeals of the march, I think this was the climax for that army; and the next day was equal to it, possibly. The heat was so intense that the dust burned us. Many of the men were falling out by the way-side, overcome by the heat. The officers put leaves, dipped in water when it could be had, into their hats as a precaution against sun-stroke. The very atmosphere was aglare with the blazing sun and it was sad to see so many men collapsing under the blasting heat; many strong men with the look of despair upon their faces, with 'death by sun-stroke,' soon to be written after their names upon the roll! Even the surgeons were too near prostrated to render the help so much needed by these suffering men. The scene on this terrible, hot march was as appalling as battle itself. I think it was equally as trying on man and beast."
On the 16th of July, the 55th Ohio took part in a reconnaissance from Sperryville to Madison Courthouse. Jackson's strike-force, the van-guard of Robert E. Lee's planned offensive against Pope's army, was only a short distance away, at Orange Courthouse and Gordonsville. The reconnaissance returned to Sperryville on the 19th of July.
Sources:
Trials and Triumphs: A Record of the Fifty-Fifth Ohio Volunteer Infantry by Hartwell Orsborne, 1904, A.C. Clurg & Co., Chicago.
War, As Viewed From The Ranks by William Keesy, 1898.