The USS Monitor was an American ironclad warship designed during the American Civil War, conceived as a response to the burgeoning conflict between the Union and the Confederacy. Launched on January 30, 1862, at the Brooklyn Navy Yard in New York, the Monitor was designed by Swedish engineer John Ericsson. This vessel was notable for its revolutionary design, which included a revolving turret that housed two large cannons, setting it apart from traditional wooden ships of the time. As tensions escalated in the Civil War, the need for more powerful naval vessels became evident, particularly after the Confederates launched their own ironclad, the CSS Virginia, which posed a considerable threat to Union blockades. The Monitor was hastily constructed as a countermeasure to this new form of naval warfare.

Upon its launch, the Monitor did not undergo extensive sea trials but was quickly deployed to engage the Virginia. This encounter would occur during the notable Battle of Hampton Roads in March. The battle marked the first clash of ironclads and would change naval warfare permanently. While the Monitor did not emerge victorious in a traditional sense, its ability to withstand heavy fire and inflict damage on the Virginia would signal a new era in naval combat, one where wooden ships were rendered obsolete. The design and capabilities of the Monitor influenced future shipbuilding practices and military strategies through the latter part of the 19th century.

The Monitor underwent several modifications during its brief service. It was equipped with steam engines and was designed to be a low-profile vessel, making it less vulnerable to enemy fire. Despite its innovative design, the Monitor was eventually lost in a storm off the coast of North Carolina in December. Its legacy, however, endured, igniting further developments in naval technology and defense strategies, especially in the context of ironclads in warfare.