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The U.S. Coast Survey and the Blockade, 1861

When the war began in the spring of 1861, the Union quickly adopted what became known as the "Anaconda Plan," so called because it proposed to strangle the South economically and militarily by closing off its seaports and controlling the Mississippi River and its tributaries. Although the plan was loudly ridiculed by some, ultimately it proved to be very effective, constricting the Confederacy in an ever-tightening binding of Federal gunboats, naval vessels and seized port facilities.

As part of the planning for this enormous naval operation, the Navy Department convened a special board to compile a report on the different parts of the Southern coastline, with special emphasis on the conditions that would influence naval and military operations. The sections of the board's report describing conditions at Mobile, Alabama and Galveston, Texas, the two ports into which Denbigh ran the blockade, are reproduced below.

Although the board was headed by a senior naval officer, Samuel F. Du Pont, the member of the board most familiar with the Gulf Coast was undoubtedly Alexander Dallas Bache (1806-1867), a West Point-trained engineer who before the war had been superintendent of the U.S. Coast Survey. Under Dallas' direction, the Coast Survey had meticulously recorded the bays, inlets and hydrographic features of the entire Gulf of Mexico. The charts compiled during Bache's tenure as superintendent (1843-1861) were the first comprehensive and scientific effort to chart the coast of Texas. And although Bache, a great-grandson of Benjamin Franklin, was (like his forebear) a native of Pennsylvania, he had substantial ties to Texas. Bache's father served in the Texas Navy aboard the steamship Zavala, and later served as a Galveston County justice of the peace, port inspector and state senator.

Mobile, Alabama

4. The coast of part of northern and western Florida and the coasts of Alabama and Mississippi, from the river Perdido to Ship Island: This section includes Mobile Bay and Mississippi Sound, with its numerous and subsidiary waters.

This is a stretch of coast of but 75 nautical miles, the only interest of which attaches to Mobile entrance, bay, and city, and to the approaches.

The bar of Mobile entrance is next to that of Pensacola in depth, having 20 feet upon it, which can be carried to the fine protected anchorage known as the Lower Fleet. From this to the city wharves 8 feet can be carried. The entrance is defended by a finished work of considerable size (Fort Morgan) at Mobile Point, on the eastern side, and by a work in progress (Fort Gaines) of smaller dimensions, on Dauphin Island Point, on the western side.

Mobile City has a population of 41,131 by the last census, and is the great cotton exporting port of the Gulf, next to New Orleans. The Mobile River, the Alabama River, and its branches, head in the upper part of the State of Alabama. A railroad connects it with Cairo, at the entrance of the Ohio into the Mississippi River.

Besides the main entrance to Mobile Bay, there is an artificial side entrance between Dauphin Island and the mainland, at Grant's Pass, with 5¼ feet at low water and about 6¾ at high. This pass was excavated through oyster reefs and mud, and has remained open. There was a light there before the rebellion. This pass is 7½ miles in a straight line from Fort Morgan, and 25 miles from the city of Mobile. Mississippi Sound has several good entrances directly from the Gulf. It is not known whether any attempt has yet been made to fortify them or the pass just mentioned. These are:

1. Through the east spit of Petit Bois a passage was cut in the hurricane of 1852, having 12 feet as the least water.

2. Horn Island Pass, between Petit Bois and Horn Island, has 16 feet water.

3. There is a fine, wide channel between Ship and Cat islands, with 21 feet least water, except upon two 17-foot lumps. This, however, is in part closed by the fort on Ship Island.

There is a good channel from Ship Island to Dauphin Island for vessels drawing not more than 15 feet.

Cat and Ship Island harbors are probably both fortified. Into the former 17 feet, and into the latter 19 feet can be carried. The possession of the eastern part of Mississippi Sound, or the blockade of the entrances, will be necessary, besides watching the main entrance of the bay, to the effective blockade of Mobile.

Unless Grant's Pass is effectually defended, or is obstructed, the defenses at Mobile may be turned by a force of suitable character.

Before speaking of the approaches to the city of Mobile we must recur to the fortifications on Ship Island, which constitute one of our principal means for closing up New Orleans.

The military possession of Ship Island is no less important to our naval operations in Mississippi Sound than to the blockade of New Orleans.

We require it as a depot of coal and provisions, as well as a harbor for repairs and refuge. The small semicircular work which was commenced by the U hired States, and has since been seized by the rebels, was scarcely above ground when the rebellion broke out. We regard it as not much more defensible than the Hatteras forts. However this may be, the entire possession of Ship Island and its substitution for Pensacola as a naval station are indispensable, and its defense might be partly naval and partly military.

The most hasty glance at the map will be sufficient to recognize at once the importance (not to be overrated) of a rigid blockade on a portion of the coast, distinguished by the geographical features which are most favorable to trade and intercourse by water, and sheltered from the destructive influence of storms by a barrier of out-lying islands.

It fortunately happens here, as elsewhere, that the blockading fleet can perform its duty strictly while it is enjoying the protection of the enemy's harbors.

We must add a word on the approach to Mobile by land.

From the Gulf shore, the nearest land approach to Mobile leads from Pascagoula 45 miles by hard, level, sandy roads through pine woods, clear of underbrush, and easily known by the telegraph poles.

Six miles out, a rough bridge of 30 feet crosses a deep, muddy stream, bordered with dense bushes.

Thence on about 30 miles farther the route is over flat country, with only scattering log houses, and a low population, to Dog River, which is 40 feet wide, muddy, and unfordable. The well-worn bridge there has probably been replaced. Yellow pine is plenty near both streams; other streams along the road are mere rivulets of fresh water.

From Dog River to Mobile the track rolls gently, showing better land (sparsely settled by uncultivated people); and at a distance of 9 miles it meets Government street, Mobile, about 2 miles west of the Mobile wharves.

There is a deep ravine on the road, perhaps not far from the Dog River.

Mobile may also be reached from Pensacola by the Perdido Bay and River: and from Portersville, Ala., a small village opposite the west end of Dauphin Island, through which the New Orleans mail once passed, having been brought from Mobile by stages and carried thence to New Orleans by steamboats. We can furnish some of the particulars concerning the route (from the archives of the Coast Survey) when they are wanted.

But we will not lengthen out this already tedious memoir.

In this paper we have treated, first, the great Delta of the Mississippi from its eastern to its extreme western boundary; and, second, in connection with it, as an inseparable part of the system of operations recommended, Mississippi Sound and Mobile, with its adjacent waters.

We have the honor to be, very respectfully, your most obedient servants,

Captain, U. S. Navy, President.

Superintendent U. S. Coast Survey, Member.

Major, U. S. Engineer, Member.

Commander, U. S. Navy, Member and Secretary.

From Official Naval Records, Series I, Vol. 16, pp. 628-30.

Galveston, Texas

5. Coast of part of Louisiana and the whole coast of Texas, from Grande Pass, Vermilion Bay, to the Rio Grande del Norte: From Vermilion Bay to the Sabine River is about 100 nautical miles, and the coast of Texas, from the Sabine to the Rio Grande, extends about 325 miles.

The chief interest of this section centers at Galveston entrance, 55 miles from the Sabine River and 270 from the Rio Grande. Galveston entrance itself is but the analogue of Charleston, [S. C.], in its depth of water, having 12 feet at low water over a shifting bar. This chief maritime city of Texas had, in 1860, but 8,117 inhabitants and a small foreign trade. The number of vessels which arrived at Galveston in 1856, from beyond the limits of the collection district, was 269, of which 27 were foreign vessels. New Orleans is the great entrepôt which it uses, from which it is distant 280 miles by the steamer route to Berwick Bay, and thence by the Opelousas, New Orleans [and Great Western] Railroad.

There are small steamers trading from Galveston up the bay and Trinity River, and to the various rivers and bays of the coast by a precarious navigation, part of which is exposed to the dangers arising from the storms of the Gulf. An efficient blockade of Galveston is, in fact, the blockade of the coast of Texas. Of the six other entrances, one, the Rio Grande, has but 4 feet on its bar at low water, and 4.9 feet at high water; Aransas Pass, 9 feet; Matagorda, 9 feet; Brazos River, 8 feet; San Luis Pass, 8 feet; Sabine Pass, 7½ feet at low water, with a rise of tide of less than one foot and a half at the several ports.

The smooth-water navigation, to be effected by connecting the sounds by artificial means, has been begun by the State of Texas, but not completed even for the minimum proposed depth.

Three or four efficient Vessels, which can take care of themselves at sea against storms and enemies, are required for the blockade of this portion of the coast, three being the least number which it would probably be safe to trust, considering the northers and hurricanes to which the coast is exposed, and the possible presence of fevers among the unacclimated crews. One of the vessels, besides, should be of the lightest draft, free to move up and down the coast, to interrupt the small commerce carried on by the interior sounds, which are nearly continuous from Galveston to the Rio Grande. A visit to Galveston, Corpus Christi, and Aransas to recover the United States movable property seized there from the Revenue and Coast Survey services, or to obtain indemnity for the seizures, would also form [one] of the objects of such an expedition. The Coast Survey hydrographic notes which we attach to this memoir are accompanied by maps and sketches showing the general character of this coast, and giving minute information in regard to the harbors and passes. We take this occasion earnestly to recommend that a Coast Survey vessel be attached to each of the principal blockading squadrons to complete, under general instructions from the Superintendent, the examination of such parts of the coast not yet surveyed in detail. The importance of this measure can not be overrated. Protection may readily be afforded to the surveying vessels without interfering at all with the regulations of the strictest blockade.

We have the honor to be, very respectfully, your most obedient servants,

Captain, U. S. Navy, President.

Superintendent U. S. Coast Survey, Member.

Major, U. S. Engineers, Member.

Commander, U. S. Navy, Member and Secretary.

From Official Naval Records, Series I, Vol. 16, pp. 654-55.


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Credits & Thank-Yous

J. Barto Arnold et al. 1998-2000, The Denbigh Project, World Wide Web,
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Monday, July 17, 2000 Revision.

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