New Hampshire approves the Twelfth Amendment to the United States Constitution, ratifying the document.

The Twelfth Amendment (Amendment XII) to the United States Constitution provides the procedure for electing the president and vice president. It replaced the procedure provided in Article II, Section 1, Clause 3, by which the Electoral College originally functioned. The amendment was proposed by the Congress on December 9, 1803, and was ratified by the requisite three-fourths of state legislatures on June 15, 1804. The new rules took effect for the 1804 presidential election and have governed all subsequent presidential elections.

Under the original rules of the Constitution, each member of the Electoral College cast two electoral votes, with no distinction made between electoral votes for president and electoral votes for vice president. The presidential candidate receiving the greatest number of votesprovided that number at least equaled a majority of the electorswas elected president, while the presidential candidate receiving the second-most votes was elected vice president. In cases where no individual won a vote from a majority of the electors, as well as in cases where multiple individuals won votes from a majority of electors but tied each other for the most votes, the House of Representatives would hold a contingent election to select the president. In cases where multiple candidates tied for the second-most votes, the Senate would hold a contingent election to select the vice president. The first four presidential elections were conducted under these rules.

The experiences of the 1796 and 1800 presidential elections showing that the original system caused the election of a President and Vice-President who were political opponents of each other, constantly acting at cross-purposes spurred legislators to amend the presidential election process to require each member of the Electoral College to cast one electoral vote for president and one electoral vote for vice president. Under the new rules, a contingent election is still held by the House of Representatives if no candidate wins a presidential electoral vote from a majority of the electors, but there is no longer any possibility of multiple candidates winning presidential electoral votes from a majority of electors. The Twelfth Amendment also lowered the number of candidates eligible to be selected by the House in a presidential contingent election from five to three, established that the Senate would hold a contingent election for vice president if no candidate won a majority of the vice presidential electoral vote, and provided that no individual constitutionally ineligible to the office of president would be eligible to serve as vice president.

New Hampshire ( HAMP-shər) is a state in the New England region of the United States. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Gulf of Maine to the east, and the Canadian province of Quebec to the north. Of the 50 U.S. states, New Hampshire is the fifth smallest by area and the tenth least populous, with slightly more than 1.3 million residents. Concord is the state capital, while Manchester is the largest city. New Hampshire's motto, "Live Free or Die", reflects its role in the American Revolutionary War; its nickname, "The Granite State", refers to its extensive granite formations and quarries. It is best known nationwide for holding the first primary (after the Iowa caucus) in the U.S. presidential election cycle.New Hampshire was inhabited for thousands of years by Algonquian-speaking peoples such as the Abenaki. Europeans arrived in the early 17th century, with the English establishing some of the earliest nonindigenous settlements. The Province of New Hampshire was established in 1629, named after the English county of Hampshire. Following mounting tensions between the British colonies and the crown during the 1760s, New Hampshire saw one of the earliest overt acts of rebellion, with the seizing of Fort William and Mary from the British in 1774. In January 1776, it became the first of the British North American colonies to establish an independent government and its own state constitution; six months later, it signed the United States Declaration of Independence and contributed troops, ships, and supplies in the war against Britain. In June 1788, it was the ninth state to ratify the U.S. Constitution, bringing that document into effect.

Through the mid-19th century, New Hampshire was an active center of abolitionism, and fielded close to 32,000 men for the Union during the U.S. Civil War. After the war, the state saw rapid industrialization and population growth, becoming a center of textile manufacturing, shoemaking, and papermaking; the Amoskeag Manufacturing Company in Manchester was at one time the largest cotton textile plant in the world. The Merrimack and Connecticut rivers were lined with industrial mills, most of which employed workers from Canada and Europe; French Canadians formed the most significant influx of immigrants, and today roughly a quarter of all New Hampshire residents claim French American ancestry, second only to Maine.

Reflecting a nationwide trend, New Hampshire's industrial sector declined after the Second World War. Since 1950, its economy has heavily diversified to include financial and professional services, real estate, education, and transportation, with manufacturing still higher than the national average. Beginning in the 1980s, its population surged as major highways connected it to the Greater Boston and led to more bedroom communities. In the 21st century, New Hampshire is among the wealthiest states in the U.S., with the seventh highest median household income and some of the lowest rates of poverty, unemployment, and crime. It is one of only nine states without an income tax, and has no taxes on sales, capital gains, or inheritance; consequently, its overall tax burden is the lowest in the U.S. after Florida. New Hampshire ranks among the top ten states in metrics such as governance, healthcare, socioeconomic opportunity, and fiscal stability.With its mountainous and heavily forested terrain, New Hampshire has a growing tourism sector centered on outdoor recreation. It has some of the highest ski mountains on the East Coast and is a major destination for winter sports; Mount Monadnock is among the most climbed mountains in the U.S. Other activities include observing the fall foliage, summer cottages along many lakes and the seacoast, motor sports at the New Hampshire Motor Speedway, and Motorcycle Week, a popular motorcycle rally held in Weirs Beach in Laconia. The White Mountain National Forest links the Vermont and Maine portions of the Appalachian Trail, and has the Mount Washington Auto Road, where visitors may drive to the top of 6,288-foot (1,917 m) Mount Washington.