Although the Mangham family came from England to Virginia by the late 1680s, most of them apparently adopted the phonetic spelling Mangum during the ensuing century. Many others eventually adopted the spelling Mangrum, apparently pronouncing the name with a bit of a trill.
The only Mangham who served from a Virginia unit during the Civil War was Pvt. John Henry Mangham, a Georgia-born Alabamian who transferred into a Virginia artillery battery while in Tennessee! Whew!
He was one of the most mysterious characters I ran across! See a photograph of his grave in Montgomery. It's now marked Willis A. Mangham, 30th Alabama, which apparently resulted from a misreading of information I provided. . .