Events January–March January 20 – Charles Elliot of the United Kingdom, and Qishan of the Qing dynasty, agree to the Convention of Chuenpi. January 26 – Britain occupies Hong Kong. Later in the year, the first census of the island records a population of about 7,500. January 27 – The active volcano Mount Erebus in Antarctica is discovered, and named by James Clark Ross. January 28 – Ross discovers the "Victoria Barrier", later known as the Ross Ice Shelf. On the same voyage, he discovers the Ross Sea, Victoria Land and Mount Terror. January 30 – A fire ruins and destroys two-thirds of the villa (modern-day city) of Mayagüez, Puerto Rico. February 4 – First known reference to Groundhog Day in North America, in the diary of a James Morris. February 10 – The Act of Union (British North America Act, 1840) is proclaimed in Canada. February 11 – The two colonies of the Canadas are merged, into the United Province of Canada. February 18 – The first ongoing filibuster in the United States Senate begins, and lasts until March 11. February – El Salvador proclaims itself an independent republic, bringing an end to the (already de facto defunct) Federal Republic of Central America. March 4 – William Henry Harrison is sworn in as the ninth President of the United States. March 9 – United States v. The Amistad: The Supreme Court of the United States rules in the case, that the Africans who seized control of the ship had been taken into slavery illegally. March 12 – , commanded by legendary captain Richard Roberts ("I'd Go to Sea in a Bathtub"), founders in rough seas, with all passengers and crew lost. April–June April 4 – President William Henry Harrison dies of pneumonia, aged 68, becoming the first President of the United States to die in office, and at one month, the American president with the shortest term served. He is succeeded by Vice President John Tyler, who becomes the tenth President of the United States. April 6 – President John Tyler is sworn in. May – The Sino-Sikh War begins. May 3 – New Zealand becomes a separate British colony, having previously been administered as part of the Colony of New South Wales. May 22 – The Georgian province of Guria revolts against the Russian Empire. June 6 – The United Kingdom Census is held, the first to record