The two Mississippi-class battleships were ordered under the terms of the 1903 naval appropriations, which stipulated a maximum designed displacement of 13,000 long tons (13,209 t).
The limit was an effort led by senior naval officers including Admiral George Dewey and Captain Alfred Thayer Mahan, who believed a force of smaller but more numerous battleships would better suit the navy's needs.
Elements in Congress also opposed the continually increasing size, and more importantly, cost of each new battleship design.
The limited displacement amounted to a reduction of 3,000 long tons (3,048 t) compared to the preceding Connecticut class, which necessitated significant compromises in speed, armament, and armor, making them poor designs unable to serve with the main fleet and led to their quick disposal.

Idaho was 382 feet (116 m) long overall and had a beam of 77 ft (23 m) and a draft of 24 ft 8 in (7.52 m).
She displaced 13,000 long tons as designed and up to 14,465 long tons (14,697 t) at full combat load.
The ship was powered by two-shaft vertical triple expansion engines and eight coal-fired Babcock & Wilcox boilers rated at 10,000 indicated horsepower (7,500 kW) and a top speed of 17 knots (31 km/h; 20 mph).
Lattice masts were installed in 1909.
She had a crew of 744 officers and enlisted men.

The ship was armed with a main battery of four 12 in (305 mm) L/45 guns in two twin turrets, one on either end of the superstructure.
Eight 8 in (203 mm) L/45 guns were mounted in four twin turrets, two on other side of the vessel amidships.
The secondary battery was rounded out with eight 7 in (178 mm) L/45 guns mounted individually in casemates along the length of the hull, two fewer than the Connecticut class.
Close-range defense against torpedo boats was protected by a battery of twelve 3 in (76 mm) L/50 guns (compared to twenty aboard the Connecticuts), six 3-pounder guns and two 1-pounder guns.
The ship's armament system was completed by two 21 in (533 mm) torpedo tubes submerged in her hull.

The ship's main armored belt was 7 to 9 in (178 to 229 mm) thick and, reduced to 4 to 7 in (100 to 180 mm) on either end.
This amounted to a two-inch reduction compared to the Connecticuts.
The main battery gun turrets had 12 in (305 mm) thick faces, mounted atop 10 in (250 mm) barbettes.
Her secondary battery was protected by 7 in (180 mm) side armor.
The forward conning tower had 9 in thick sides.
The two Mississippi-class battleships were ordered under the terms of the 1903 naval appropriations, which stipulated a maximum designed displacement of 13,000 long tons (13,209 t). The limit was an effort led by senior naval officers including Admiral George Dewey and Captain Alfred Thayer Mahan, who believed a force of smaller but more numerous battleships would better suit the navy's needs. Elements in Congress also opposed the continually increasing size, and more importantly, cost of each new battleship design. The limited displacement amounted to a reduction of 3,000 long tons (3,048 t) compared to the preceding Connecticut class, which necessitated significant compromises in speed, armament, and armor, making them poor designs unable to serve with the main fleet and led to their quick disposal.
Idaho was 382 feet (116 m) long overall and had a beam of 77 ft (23 m) and a draft of 24 ft 8 in (7.52 m). She displaced 13,000 long tons as designed and up to 14,465 long tons (14,697 t) at full combat load. The ship was powered by two-shaft vertical triple expansion engines and eight coal-fired Babcock & Wilcox boilers rated at 10,000 indicated horsepower (7,500 kW) and a top speed of 17 knots (31 km/h; 20 mph). Lattice masts were installed in 1909. She had a crew of 744 officers and enlisted men.
The ship was armed with a main battery of four 12 in (305 mm) L/45 guns in two twin turrets, one on either end of the superstructure. Eight 8 in (203 mm) L/45 guns were mounted in four twin turrets, two on other side of the vessel amidships. The secondary battery was rounded out with eight 7 in (178 mm) L/45 guns mounted individually in casemates along the length of the hull, two fewer than the Connecticut class. Close-range defense against torpedo boats was protected by a battery of twelve 3 in (76 mm) L/50 guns (compared to twenty aboard the Connecticuts), six 3-pounder guns and two 1-pounder guns. The ship's armament system was completed by two 21 in (533 mm) torpedo tubes submerged in her hull.
The ship's main armored belt was 7 to 9 in (178 to 229 mm) thick and, reduced to 4 to 7 in (100 to 180 mm) on either end. This amounted to a two-inch reduction compared to the Connecticuts. The main battery gun turrets had 12 in (305 mm) thick faces, mounted atop 10 in (250 mm) barbettes. Her secondary battery was protected by 7 in (180 mm) side armor. The forward conning tower had 9 in thick sides.
Greek battleship Lemnos