In 1614 the Dutch explorer Adriaen Block sailed through Long Island Sound and explored the Connecticut River. The Dutch built a small fort in 1633 on the site of present-day Hartford, but they abandoned it in 1654 as English settlers moved into the area in increasing numbers.
Edward Winslow of Plymouth Colony was apparently the first English colonist to visit (1632) Connecticut, and in 1633 members of the Plymouth Colony established a trading post on the site of Windsor. This small Pilgrim enterprise was soon absorbed by Puritan settlers from the Massachusetts Bay Company. These settlers had been attracted to the area by the excellent reports brought back by one of their members, John Oldham, in 1633. Oldham returned to the Connecticut area in 1634 and established still another trading post, which became Wethersfield. The following year Puritans flocked in great numbers to the Connecticut River Valley.
In 1636, Thomas Hooker and his congregation left Newtown and settled near the Dutch trading post that had been established on the site of Hartford. The Pequot people resisted white settlement, but they were defeated by the English in the short Pequot War of 1637. Relations remained relatively peaceful until King Philip's War in 1675–76. In 1638–39 representatives of the three Connecticut River towns—Hartford, Windsor, and Wethersfield—met at Hartford and formed the colony of Connecticut. They also adopted the Fundamental Orders, which established a government for the colony.
A second colony, Saybrook, had been established at the mouth of the Connecticut River in 1635 by an English group. The colony's founders (who included Viscount Saye and Sile and Baron Brooke, for whom the colony was named) sold the Saybrook settlement to Connecticut colony in 1644. Connecticut's population expanded gradually, and by 1662 the colony included over a dozen towns, including Saybrook, New London, Fairfield, and Norwalk, as well as East Hampton and Southampton on Long Island. Another Puritan settlement, New Haven, was established in 1638. It was not connected with Connecticut colony.
In 1643, New Haven and Connecticut colonies joined with Massachusetts Bay colony and Plymouth colony to form the New England Confederation, a loose union for mutual defense. In 1662, Connecticut sent its governor, John Winthrop (1606–76), to London to secure a royal charter for the colony. He obtained the charter, by which Connecticut won its legal right to exist as a corporate colony and also acquired New Haven.
The years from 1750 to 1776 saw much bitter disagreement between radicals and conservatives in the colony. In 1776, the patriot governor, Jonathan Trumbull, was reelected almost unanimously (Connecticut and Rhode Island were the only colonies privileged to elect their chief executives), and he was the only governor of any colony to be retained in office after the outbreak of the American Revolution. There was little fighting in Connecticut during the Revolution—skirmishes at Stonington (1775), Danbury (1777), New Haven (1779), and New London (1781)—even though the state was the principal supply area for the Continental Army.
After the war the state relinquished (1786) to the United States its claims to western land, except for the Western Reserve (an area in Ohio). This claim was retained until part of the land was given to Connecticut citizens in 1792 and the remainder sold in 1795. In 1799, Connecticut's long dispute with Pennsylvania over the Wyoming Valley was finally settled. Connecticut was one of the first states to approve the U.S. Constitution (see Constitutional Convention).
The Embargo Act of 1807, passed during the administration of Thomas Jefferson, was vehemently denounced throughout New England; the ports on Long Island Sound and on the Connecticut River had developed a lively carrying trade with which the embargo interfered. The War of 1812 was also so unpopular that New England Federalists, meeting at the Hartford Convention in late 1814, considered secession. In 1818 the Jeffersonians came into power in the state, and a new constitution, replacing the old charter of 1662, was adopted. It disestablished the Congregational Church and greatly extended the franchise, although universal manhood suffrage was not proclaimed until 1845.
Meanwhile, after Connecticut's shipping industry had been ruined by the embargo and the war, the state turned to manufacturing. Artisans and craftsmen had become increasingly numerous in late colonial days, and from native iron ore Connecticut forges had produced guns for the Patriot soldiers. Modern mass production had its beginning in the state when Eli Whitney, probably the best known of Connecticut's inventors, established (1798) at New Haven a firearms factory that began making guns with standardized, interchangeable parts. Earlier, in 1793, he had invented and manufactured the cotton gin at New Haven. The manufacture of notions (buttons, pins, needles, metal goods, and clocks) gave rise to the enterprising "Yankee peddler," who, with horse and cart, traveled the nation hawking his wares. Connecticut's insurance industry also developed during this period, and in 1810 the Hartford Fire Insurance Company was established.
Connecticut, which had placed limitations on slavery in 1784 and abolished it in 1848, supported the Union during the Civil War with nearly 60,000 troops. During and after the war, industry expanded greatly. Immigration provided a cheap labor supply as English, Scottish, and many Irish immigrants, who had arrived in large numbers even before the war, were followed by French Canadians and, in the late 19th and early 20th cent., by Italians, Poles, and others.
During World Wars I and II Connecticut prospered, providing munitions and other supplies for the war effort. Between the two wars, however, the Great Depression left many unemployed. Connecticut's industries continued to grow and develop in the years following World War II. In 1954 the world's first nuclear-powered submarine was launched at Groton, and guns, helicopters, and jet engines were among key manufactures of the cold war period.
During the 1970s, as manufacturing began to decline, Connecticut's heavy industry–dependent major cities fell into a state of decay. The growth of financial, insurance, real estate, and service industries, however, helped make Connecticut one of the wealthiest states in the nation; many of these business moved to the state from New York. This wealth has been enjoyed primarily by the state's affluent suburbs, while the central cities have further crumbled, as evidenced by Bridgeport's bankruptcy filing in 1991. The development of Native-American-owned casinos in SE Connecticut during the 1990s supplanted defense industries as the main economic engine in that region. In 2012 many of the state's coastal communities suffered significant flooding during Hurricane Sandy.