The Library Of Congress (LOC) updated the Historic Newspaper section recently (it pays to keep checking back). I found another article for knitting socks. This is the earliest I've found so far...and I keep on looking for directions both Union and Confederate.
The Philadelphia Inquirer [PA] October 1, 1861
WOOLEN SOCKS FOR THE ARMY.—the following directions, which have been furnished by a lady of much experience, may prove useful to those who will engage in knitting woolen socks for the army. The yarn should be bluish gray, No. 22, and the needles, No. 14 or No. 15.
Set up twenty-seven stitches on each needle; knit two plain and two seam rows alternately, until the ribbing is three inches long; then knit plain seven inches for the leg, remembering to seam one stitch at the end of one needle. To form the heel, put twenty stitches on two of the needles, and forty-one on the other—the seam stitch being in the middle. Knit the first row plain, the next row seam, and so alternately until the heel is three inches long; then narrow on the plain row each side of the seam stitch for five plain rows, which will leave thirty-one stitches. To close the heel, knit the last seam row to the middle of the needle, knit the seam stitch plain, then fold the two needles together, and with another needle take off the seam stitch. Then knit a stitch from both needles at once, and bind the seam stitch over it. Continue knitting in this manner until but one is left and the heel closed. Take up as many stitches as there are rows around the heel; knit one round plain; then widen every fifth stitch on the heel needles. Narrow once on every round at each side of the foot until there are twenty-seven stitches on each needle; knit plain six inches, narrow at the beginning and end of each needle on every third round, till you have seventeen stitches on each; then narrow every second round till you have seven—then every round until the foot is closed. One pound of yarn, costing from seventy-five cents to one dollar, will furnish four pairs of socks.