ARMY OF THE POTOMAC,
Washington, D. C., March 29, 1862.
GENERAl,: I have the honor to submit the following information relative to the forces and defenses at Yorktown, Williamsburg, Bethel, &c., as extracted from various reports previously addressed to you from these headquarters:
That from the statement made by James H. Maurice, deserter from the Second Florida Regiment, reported on to you on February 1, I am enabled to select the following concerning defenses on the Yorktown Peninsula, to wit:
FORTS, DEFENSES, ETC., NEAR YORKTOWN VA.
Fort Grafton is 4 miles southeast by south from Yorktown and one-quarter of a mile back of an inlet from York River; contains four 32-pounders; that in the northeast corner being rifled and protecting a powder magazine. Artillery fort, adapted for field pieces, three-quarters of a mile southeast from Fort Grafton, 4 3/4 miles southeast from Yorktown, on an old road leading from this fort to Back Creek. Breastwork for cannon on the north side of Poquosin Creek, by an old mill. Yorktown is surrounded by a breastwork, on which 32-pounders are mounted, the number of which was not known by informant. That the magazine is in Cornwallis Cave, at the foot of the bluff on which the town is built. That in immediate proximity to this magazine is a fort containing six guns, not rifled; is covered with sods for concealment, and cannot be seen until close at hand. Fort half a mile south-southwest from Yorktown, mounting three 32-pounders, one rifled; fort three-quarters of a mile south-southwest from Yorktown, mounting two 32-pounders. Rifle pit from the bridge on Back Creek northwest to the shore and along the shore westerly; that it is concealed, the earth dug from it being thrown into the water. Fort at Gloucester, opposite Yorktown, contains two 10-inch columbiads, one rifled cannon of European manufacture, and two or three 32-pounders—in all five or six guns. Informant was sufficiently near to perceive that these guns were genuine. Informant was told, and understood from general report, that Williamsburg was well fortified, but cannot speak on that point from personal observation.
That from the statement made by William H. Ringgold, who left Gloucester November 6, 1861, reported on to you on December 2, 1861, I am enabled to present the following concerning the defenses on the Yorktown Peninsula, to wit:
That at Gloucester Point proper, York River, is a battery of nine 32-pounder columbiads, pointing up, down, and across the river; that on the bluff encircling Gloucester Point is a continuous embankment about 1 miles in length from the river above to the river below; that this embankment was used as a sentinel-walk, and that on the inside thereof was a single gun, commanding the country road coming from the north. That on Bryant’s plantation, 2 ½ miles below Gloucester Point, are two masked batteries, commanding the river, each containing one gun, one battery being situated on each end of the plantation. That around Yorktown on the land side is a continuous embankment, about 3 miles in length, and mounted with heavy columbiads, commanding all approaches to the town; that within the embankment or breastwork are  minor intrenchments. That at Yorktown there was a battery, consisting of five heavy columbiads, mounted on the heights of the town, directly opposite the Gloucester batteries, and commanding the river. That what has been called Cornwallis Cave was used as a magazine for ammunition; that the principal magazine was then (November 5) on the bluff, about 75 yards back of Cornwallis Cave, in an embankment on the upper side of the old road leading up into the town; that under the bluff just below Cornwallis Cave, concealed from upward-bound vessels behind a point on the river, is a battery of four or five short guns of large caliber, supposed to be shell guns; that this battery cannot be seen by vessels ascending the river until they have passed the point of land concealing it and are directly opposite the said battery. That there are iron gun-carriages at Ship Point, 8 miles below Toos Point; that up to November 5 there were no batteries on the York River Railroad between West Point and Richmond. That there were no fortifications or batteries on York River above Yorktown and Gloucester Point, or between the York and Rappahannock Rivers, except at Gloucester Point. That on December 9, 1861, my operative conversed with a lieutenant in General Magruder’s command, said lieutenant being then on furlough at Richmond; that my operative asked the lieutenant if any further defenses had been made at West Point or on the York River within a month, and that the lieutenant replied, “No;” adding that the defenses at Gloucester Point and Yorktown were considered sufficient to protect the river.
That the statement of James H. Maurice, under date of February 1, concerning the forces on the James and York River Peninsula, is substantially as follows, to wit:
Encamped 3 miles southwest of Yorktown—Second Florida, Colonel Ward, 700 to 800 men; Sixteenth Georgia, Colonel Cobb; Thirteenth Louisiana, Colonel Sulakowski. Cobb’s Legion, 4 ½ miles south of Yorktown and 2 miles southeast from the Second Florida. Fifty-fifth Virginia, 4½ miles south-southeast of Yorktown and half a mile back from the head of the creek. Fifth Virginia Artillery, Fort Grafton, 4miles south-southeast of Yorktown. Two regiments, names not known, on the Cornwallis battle-ground. Three regiments immediately south of Yorktown. Several regiments at Williamsburg.
That William H. Ringgold, an intelligent colored man, in report addressed to you December 2, 1861, specifies the following regiment as being on the Yorktown Peninsula and at Gloucester Point:
Sixth Georgia Infantry, Colonel Colquitt, numbering 1,000 men, within the intrenchments at Yorktown above described. Louisiana Zouaves, numbering about 950, encamped a short distance below Yorktown. Second Alabama Infantry, 1,050 men, 3 miles from Yorktown, on the road to Hampton. Fifth North Carolina Infantry, 800 men, 8 miles from Yorktown, on the road to Big Bethel. Eighth Alabama Infantry, Colonel Winston, 1,000 men, near Big Bethel Church. Cobb’s Legion, 5 or 6 miles from Big Bethel Church, 2 miles west of the road to Hampton and opposite Little Bethel. This Legion consists of about 400 cavalry, armed with Maynard’s rifles, and 600 infantry, all from Georgia., commanded by Thomas C. Cobb. Several Louisiana regiments at Williamsburg. At Gloucester Point, 5,000 infantry, 160 cavalry, and two companies of artillery. That the total rebel force on the York and James River Peninsula was estimated by the rebels at 25,000 men. That there is a telegraph from Richmond to West Point, also from Yorktown and Great Bethel to Richmond via James River and  Grove Wharf. That there is much Union feeling among the poorer classes on the York and Rappahannock Rivers, especially among the oystermen and fishermen.
All of which is respectfully submitted by your obedient servant,
E. J. ALLEN [ALLEN PINKERTON].
Maj. Gen. GEORGE B. MCCLELLAN,
Commanding U. S. Army.
Official Records of the Rebellion: Volume Eleven, Chapter 23, Part 1: Peninsular Campaign: Reports, pp.266-268
web page Rickard, J (19 November 2006), http://www.historyofwar.org/source/acw/officialrecords/vol011chap023part1/00013_02.html