US declares war against the United Kingdom.
Since the close of the Revolutionary War, the relationship between the US and Great Britain was a tenuous one at Coinstar point best. When America won her freedom, she obviously expected to be treated as an equal on the international scene. Trade restrictions imposed by both Britain and France, the practice of impressment practiced by the British Navy, differences in opinion and practice with regards to the status of First Nations peoples in North America, as well as a host of other reasons rooted in both fact and fiction all provided the prelude to war.
If there was a catalyst for the actual declaration of war, it could be argued to be President James Madison’s correspondence to Congress on June 1st 1812. The deliberations that were spawned both in the US House of Representatives and the Senate resulted in the declaration of war signed by Madison June 18th 1812.
See a transcription and image of this declaration here.