Several boards have been appointed by US presidents or Congress to evaluate the US defensive fortifications, primarily coastal defenses

Seacoast Defense (US)

Seacoast defense was a major concern for the United States from its independence until World War II. Before airplanes, America's enemies could only reach her from the sea, making coastal forts an economical alternative to standing armies or a large navy. After the 1940s it was recognized that fixed...

 near strategically important harbors on the US shores, its territories, and its protectorates.

Endicott Board

In 1885 US President Grover Cleveland

Grover Cleveland

Stephen Grover Cleveland was the 22nd and 24th president of the United States. Cleveland is the only president to serve two non-consecutive terms and therefore is the only individual to be counted twice in the numbering of the presidents...

 appointed a joint Army, Navy and civilian board, headed by Secretary of War William Crowninshield Endicott

William Crowninshield Endicott

William Crowninshield Endicott was an American politician and Secretary of War in the Administration of President Grover Cleveland.-Life and work:...

, known as the Board of Fortifications (now usually referred to simply as the Endicott Board). The findings of the Board in its 1886 report illustrated a grim picture of neglect of America's coast defenses and recommended a massive $127 million construction program for a series of new forts with breech-loading cannons, mortars, floating batteries, and submarine mines for some 29 locations on the US coast. Coast Artillery fortifications built between 1885 and 1905 are often referred to as Endicott Period fortifications.

Prior efforts at harbor defense construction had ceased in the 1870s. Since that time the design and construction of heavy ordnance had advanced rapidly, including the development of superior breech-loading and longer-range cannon, making U.S. harbor defenses obsolete. In 1883, the Navy had begun a new construction program with an emphasis on offensive rather than defensive warships, and many foreign powers were building more heavily armored warships with larger guns. These factors combined to create a need for improved coastal defense systems.

The Endicott Board's recommendations led to a large-scale modernization program of harbor and coast defenses in the United States, including the construction of modern reinforced concrete fortifications and the installation of new batteries of large-caliber (12-inch, 10-inch, 8-inch, and 6-inch) breech-loading rifled artillery and mortars. Fields of electrically controlled submarine mines were also a critical component of the new defenses, as were smaller guns (less than 5-inch caliber) used to protect the mine fields from minesweeping vessels and the larger guns from land attack.

The fortifications constructed as part of this program were a departure from the traditional masonry forts concealing massed batteries of smooth-bore cannon that had dominated U.S. harbor defense for most the 19th century. Instead, smaller batteries of up to four large caliber rifled guns each were installed in well-constructed emplacements hidden behind earth-covered concrete parapets. Most long-range, large-caliber rifles were mounted on disappearing carriages

Disappearing gun

A disappearing gun is a type of heavy artillery for which the gun carriage enabled the gun to rotate backwards and down into a pit protected by a wall or a bunker after it was fired...

 that would allow a gun to be raised to fire, but otherwise remain protected from the enemy's view or fire behind a protective parapet. Some large guns and most smaller guns were mounted on less expensive barbettes or pedastals(see table below).

Taft Board

In 1905, after the experiences of the Spanish-American War

Spanish-American War

The Spanish–American War was a conflict in 1898 between Spain and the United States, effectively the result of American intervention in the ongoing Cuban War of Independence...

, President Theodore Roosevelt appointed a new board, under secretary of war William Howard Taft

William Howard Taft

William Howard Taft was the 27th President of the United States and later the tenth Chief Justice of the United States...

. They updated some standards and reviewed the progress on the Endicott Board's program. Most of the changes recommended by the Taft Board were technical, such as adding more searchlights, electrification (lighting, communications, and projectile handling), and more sophisticated optical aiming techniques. The Board also recommended fortifications in territories acquired from Spain (Cuba and the Philippines), as well as Hawaii, and a few other sites. Defenses in Panama were authorized by the Spooner Act

Spooner Act

The Spooner Act of 1902 authorized purchasing the assets of the French Panama Canal Company, provided that a treaty could be negotiated with New Granada .-External links:...

 of 1902. The Taft program fortifications differed slightly in battery construction and had fewer numbers of guns at a given location than those of the Endicott program.

World War I and later

By the time of the First World War, many of the Endicott and Taft era forts had become obsolete due to the increased range and accuracy of naval weaponry and the advent of aircraft. In the 1920s and 1930s, most U.S. coast defense facilities were put on "maintenance" status, a type of "mothballing." In the late 1930s and early 1940s, a new program of construction added huge 16-inch gun batteries, as well as rapid-firing 6-inch and 90 mm guns guns (for use against motor torpedo boat

Motor Torpedo Boat

Motor Torpedo Boat was the name given to fast torpedo boats by the Royal Navy, and the Royal Canadian Navy.The capitalised term is generally used for the Royal Navy boats and abbreviated to "MTB"...

s) to many harbors' defenses, and large fields of submarine mines were still being deployed as well. But as it became clearer that the U.S. was unlikely to face seaborne attack, these defenses were largely discontinued (by 1945), and were decommissioned altogether after 1946.

Table of guns by caliber and carriage types

The following is summarized from American Seacoast Defenses, edited by Mark Berhow, with pages referenced from the rows. The units column reflects the lower of the original emplacements or the carriages built, since some emplacements were not armed and some carriages not used. Carriage models after 1905 are not included in the Endicott Era table.

Model	Carriage	Tube	Caliber	Units	Page
M1901	disappearing	rifle	12 inch	13	150
M1897	disappearing	rifle	12 inch	35	148
M1897	Altered	rifle	12 inch	3	146
M1896	Mortar	Mortar	12 inch	308	140
M1896	disappearing	rifle	12 inch	27	138
M1892	disappearing	rifle	12 inch	28	136
M1891	Mortar	Mortar	12 inch	86	134
M1888	lift	rifle	12 inch	2	130
M1901	disappearing	rifle	10 inch	16	128
M1896	disappearing ARF	rifle	10 inch	3	126
M1896	disappearing	rifle	10 inch	74	124
M1894	disappearing	rifle	10 inch	35	122
M1893	barbette	rifle	10 inch	9	120
M1896	disappearing	rifle	8 inch	38	110
M1894	disappearing	rifle	8 inch	26	108
M1892	barbette	rifle	8 inch	9	106
M1905	disappearing	rifle	6 inch	33	100
M1903	disappearing	rifle	6 inch	90	98
M1900	pedestal	rifle	6 inch	44	96
M1898	disappearing	rifle	6 inch	29	94
Armstrong	pedestal	rifle	6 inch	8	92
M1903	pedestal	rifle	5 inch	20	90
M1896	pilar	rifle	5 inch	32	88
Armstrong	pedestal	rifle	4.72 inch	34	86
Army/Navy	pedestal	rifle	4 inch	4	84
M1903	pedestal	rifle	3 inch	101	74
M1902	pedestal	rifle	3 inch	60	72
M1898	parapet	rifle	3 inch	111	70