Marker Logo HMdb.org THE HISTORICAL
MARKER DATABASE
“Bite-Size Bits of Local, National, and Global History”
“Bite-Size Bits of Local, National, and Global History”
Tierra Verde in Pinellas County, Florida — The American South (South Atlantic)
 

12-inch Seacoast Mortar: Model 1890-M1

 
 
12-inch Seacoast Mortar: Model 1890-M1 Marker image. Click for full size.
By Cosmos Mariner, February 4, 2015
1. 12-inch Seacoast Mortar: Model 1890-M1 Marker
Inscription.  These 12-inch mortars were manufactured at the Watervliet Arsenal, Watervliet, New York in 1901. The carriages are the Model 1896 and were manufactured by the American Hoist and Derrick Company, St. Paul, Minnesota.

The fortification you are standing in is known as Battery Laidley, in honor of Colonel Theodore T.S. Laidley, who had served in the Mexican and Civil Wars and died in Florida. In August, 1902, eight mortars were mounted. However, the weapons were not test-fired until November 19 & 20, 1903, (five years after the fort's foundations were laid). The mortars stood ready to defend the harbor of Tampa Bay but never fired a shot at an enemy. The only time they were fired was during practice.

In 1917, four of the eight mortars were dismounted and shipped to Fort Rosecrans, San Diego, California for coastal defense. After World War I, many weapons such as these were melted down to be converted to other types of weaponry. Today Fort De Soto has the only 12-inch seacoast mortars, Model 1890-M1, in the continental United States. The only other ones in the world are on the island of Corregidor in the Philippines.


Length,
12-inch Seacoast Mortar Marker (<i>wide view; marker visible at center of wall, between mortars</i>) image. Click for full size.
By Cosmos Mariner, February 4, 2015
2. 12-inch Seacoast Mortar Marker (wide view; marker visible at center of wall, between mortars)
overall: 161 inches
Length, muzzle to breech face: 141 inches
Length of bore in calibers: 10
Maximum diameter of chamber: 12.5 inches
Total weight w /carriage: 138,000 pounds
Recoil mechanism, type: Hydraulic
Length of recoil: 23 inches
Recuperating mechanism, type: 5 columns of springs
Maximum elevation: 70 degrees
Minimum elevation: 45 degrees
Traverse: 360 degrees
Powder charge: Nitro cellulose
Maximum charge: 65 pounds
Maximum range: 6.82 miles
Projectile sizes: 800, 824 & 1046 pounds

Artillery spotters, in towers, directed the firing of the weapons. They relayed readings, by telephone, to the relocating room; then the information was transmitted to the data booths just behind the gun pits. The data was interpreted there and posted to the twelve-man mortar crews by slate boards. A floating target was pulled by a small ship during practice firings at Fort De Soto. When fired, the projectile could penetrate six inches of a ship's steel deck at a range of six miles.
 
Location. 27° 36.916′ N, 82° 44.157′ W. Marker is in Tierra Verde, Florida, in Pinellas County. Marker can be reached from Anderson Boulevard (State Highway 679) 1˝ miles west of Pinellas Bayway South, on the left when traveling west. Touch for map.
12-inch Seacoast Mortar: Model 1890-M1<br>(<i>lowered into loading position</i>) image. Click for full size.
By Cosmos Mariner, February 4, 2015
3. 12-inch Seacoast Mortar: Model 1890-M1
(lowered into loading position)
Marker is located within Battery Laidley at Fort De Soto Park, just north of the Gulf Fishing Pier parking lot. Marker is at or near this postal address: 3500 Pinellas Bayway South, Saint Petersburg FL 33715, United States of America. Touch for directions.
 
Other nearby markers. At least 8 other markers are within 6 miles of this marker, measured as the crow flies. Fort De Soto Batteries and Military Post (within shouting distance of this marker); Spanish-American War Cannons from Egmont Key (within shouting distance of this marker); Spanish American War Memorial (within shouting distance of this marker); Fort De Soto Quartermaster Storehouse Museum (about 600 feet away, measured in a direct line); Tierra Verde Mound (approx. 3.8 miles away); Zephaniah Phillips' Homestead Site (approx. 5 miles away); "Pass-A-Grille" (approx. 5.1 miles away); Passage Key (approx. 5.6 miles away). Touch for a list and map of all markers in Tierra Verde.
 
Also see . . .
1. 12-inch Coast Defense Mortar (Wikipedia). The 12-inch coast defense mortar was a weapon of 12-inch (305 mm) caliber emplaced during the 1890s and early 20th century to defend US harbors from seaborne attack. The M1890 M1 (Model of 1890, Modification 1) 12-inch mortar was one of the most powerful coast artillery pieces of its era, and was the most common type emplaced to guard U.S. harbors. The M1890M1 mortar was most
12-inch Seacoast Mortar: Model 1890-M1<br>(<i>fully elevated into firing position</i>) image. Click for full size.
By Cosmos Mariner, February 4, 2015
4. 12-inch Seacoast Mortar: Model 1890-M1
(fully elevated into firing position)
often installed on an M1896 carriage. The mortar and its carriage weighed a total of 78.5 tons. (Submitted on April 9, 2019, by Cosmos Mariner of Cape Canaveral, Florida.) 

2. Seacoast Artillery In Action. This film clip from around 1915 shows a firing drill on the 12-inch mortars of Battery Howe, part of the harbor defenses of San Francisco. Heavy shells (on shell carts) being wheeled up to the breeches of the mortars and rammed home, the powder bags being tossed into the breeches after them, the crew clearing the immediate area while the chief of the breech raises his arm to indicate "ready to fire," and the mortars being fired electrically from outside the area pictured. The shock wave from firing one of these huge mortars was often so strong that it knocked doors off nearby magazines and barracks, and broke windows in nearby neighborhoods. (Submitted on April 9, 2019, by Cosmos Mariner of Cape Canaveral, Florida.) 
 
Categories. Forts, CastlesWaterways & Vessels
 
12-inch Seacoast Mortar: Model 1890-M1 Barrel (<i>rifling clearly visible inside</i>) image. Click for full size.
By Cosmos Mariner, February 4, 2015
5. 12-inch Seacoast Mortar: Model 1890-M1 Barrel (rifling clearly visible inside)
Battery Laidley Data Booth with Slate Firing Board image. Click for full size.
By Cosmos Mariner, February 4, 2015
6. Battery Laidley Data Booth with Slate Firing Board
Model 1890-M1 Diagram (<i>located near marker, within Battery Laidley exhibit</i>) image. Click for full size.
7. Model 1890-M1 Diagram (located near marker, within Battery Laidley exhibit)
12-inch steel mortar, M.1890MI. Mounted on spring return carriage, M.1896, similar to the ones at Fort De Soto. Photography is from the book, The Service of Coast Artillery, by Hines and Ward, 1910.
Model 1890-M1 Letter (<i>1989 Army letter, located near marker, within Battery Laidley exhibit</i>) image. Click for full size.
8. Model 1890-M1 Letter (1989 Army letter, located near marker, within Battery Laidley exhibit)
...To our knowledge these are the only 12” Seacoast mortars mounted on carriages in the continental U.S. The only other mortars we know of are in Corregidor, in the Philippines.
 
More. Search the internet for 12-inch Seacoast Mortar: Model 1890-M1.
 
Credits. This page was last revised on April 9, 2019. This page originally submitted on April 8, 2019, by Cosmos Mariner of Cape Canaveral, Florida. This page has been viewed 43 times since then. Photos:   1, 2, 3. submitted on April 8, 2019, by Cosmos Mariner of Cape Canaveral, Florida.   4. submitted on April 9, 2019, by Cosmos Mariner of Cape Canaveral, Florida.   5. submitted on April 8, 2019, by Cosmos Mariner of Cape Canaveral, Florida.   6. submitted on April 9, 2019, by Cosmos Mariner of Cape Canaveral, Florida.   7, 8. submitted on April 8, 2019, by Cosmos Mariner of Cape Canaveral, Florida.
Paid Advertisement We are suspending Amazon.com advertising until they remove an ad for a certain book from circulation. A word in the book’s title has given rise to number of complaints. The word is inappropriate in school classroom settings.