Maryland is bounded on the north by Pennsylvania; on the west by West Virginia; on the north and east by Delaware and the Atlantic Ocean; and on the south, across the Potomac River, by Virginia. The mid-portion of this border is interrupted on the Maryland side by Washington, DC, which sits on land originally part of Maryland. The Chesapeake Bay nearly bisects the state, and the counties east of the bay are known collectively as the Eastern Shore. A portion of extreme western Maryland in Garrett County is drained by the Youghiogheny River, as part of the watershed of the Mississippi River, while the remainder of the state drains, via the Bay, into the Atlantic Ocean. So prominent is the Chesapeake in Maryland's geography and economic life that there has been periodic agitation to change the state's official nickname to "Bay State", a name currently used by Massachusetts.

The highest point in Maryland is Hoye Crest on Backbone Mountain, which is the southwest corner of Garrett County, near the border with West Virginia and near the headwaters of the North Branch of the Potomac. In western Maryland, about two-thirds of the way across the state, is a point at which the state is only two miles (3 km) wide. This geographical curiosity, which makes Maryland the narrowest state, is located near the small town of Hancock, and results from Maryland's northern and southern boundaries being marked by the Mason-Dixon Line and the north-arching Potomac River, respectively.

The Delmarva Peninsula comprises the Eastern Shore counties of Maryland, the entire state of Delaware, and two counties of Virginia, which together form a long extension down the Atlantic seaboard. One of the most noted features of Delmarva is Maryland's Assateague Island, on the Atlantic, with its herd of feral ponies accustomed to the seashore.

On March 25, 1634, Lord Baltimore sent the first settlers into this area, which would soon become one of the few predominantly Catholic regions in the British Empire (another was Newfoundland, where religious disputes led to the first flag's coloring). Maryland was also one of the key destinations of tens of thousands of British convicts. The Maryland Toleration Act of 1649 was one of the first laws that explicitly dictated religious tolerance (as long as it was Christian). The act is sometimes seen as a precursor to the First Amendment.

Based on an incorrect map, the royal charter granted Maryland the Potomac River and territory northward to the fortieth parallel. This proved a problem, because the northern boundary would put Philadelphia, the major city in Pennsylvania, within Maryland. The Calvert family, which controlled Maryland, and the Penn family, which controlled Pennsylvania, engaged two surveyors, Charles Mason and Jeremiah Dixon, to survey what became known as the Mason-Dixon line, which would form the boundary between their two colonies and would later become the dividing line between North and South.

After Virginia made the practice of Anglicanism mandatory, a large number of Puritans migrated from Virginia to Maryland, and were given land for a settlement called Providence (now Annapolis). In 1650, the Puritans revolted against the proprietary government and set up a new government that outlawed both Catholicism and Anglicanism. This lasted until 1658, when the Calvert family regained control and re-enacted the Toleration Act. However, after England's "Glorious Revolution" of 1688, when William of Orange and his wife Mary came to the throne and firmly established the Protestant faith in England, Catholicism was again outlawed in Maryland, until after the Revolutionary War. Many wealthy plantation owners built chapels on their land so they could practice their Catholicism in relative secrecy. During the persecution of Maryland Catholics by the Puritan revolutionary government, all of the original Catholic churches of southern Maryland were burned down.

St. Mary's City was the largest site of the original Maryland colony, and was the seat of the colonial government until 1708. St Mary's is now an archaeological site, with a small tourist center. In 1708 the seat of government was moved to Providence and renamed Annapolis in honor of Queen Anne.

Maryland was one of the thirteen colonies that revolted against British rule in the American Revolution, and became the seventh state admitted to the US after ratifying the new Constitution. The following year, in December of 1790, Maryland ceded land selected by President George Washington to the federal government for the creation of Washington, D.C.

During the War of 1812, the British military attempted to capture the port of Baltimore, which was protected by Fort McHenry. It was during this bombardment that the Star Spangled Banner was written by Francis Scott Key.

Despite strong support for the cause of the Confederate States of America, Maryland did not secede during the American Civil War, in part due to precautions taken by the government in Washington, D.C. President Lincoln suspended several civil liberties, including the writ of habeas corpus, ordered US troops to place artillery on Federal Hill to directly threaten the city of Baltimore and helped ensure the election of a new pro-union governor and legislature. President Lincoln even went so far as to jail certain pro-south members of the state legislature at Fort McHenry including, ironically, the grandson of Francis Scott Key. The Constitutionality of these actions is still a source of controversy and debate. Because Maryland had not seceded from the Union, it was exempted from the anti-slavery provisions of the Emancipation Proclamation (The Emancipation Proclamation only applied to states in rebellion). A constitutional convention was held during 1864 that culminated in the passage of a new state constitution on November 1 of that year. Article 24 of that document outlawed the practice of slavery. The right to vote was extended to non-white males in 1867.

Power in Maryland is divided among three branches of government: executive, legislative, and judicial. Maryland's bicameral legislature called the General Assembly is composed of a House of Delegates and Senate. Maryland's governor is unique in the United States as the office is vested with significant authority in budgeting. The legislature may not increase the governor's proposed budget expenditures. Unlike most other states, significant autonomy is granted to many of Maryland's counties.

Most of the business of government is done in Annapolis, the state capital. Virtually all state and county elections are held in even-numbered years not divisible by four, in which the President of the United States is not elected - this, as in other states, is intended to divide state and federal politics.

Since pre-Civil War times, Maryland politics has been largely controlled by the Democrats. In the last decade, however, Republicans have made inroads in the state, including the election of the first Republican governor in almost four decades, and larger numbers of new voters are classifying themselves as independents. Blue-collar "Reagan Democrats" frequently vote Republican. Maryland is nonetheless well-known for its liberalism and loyalty to the Democratic Party, especially inside metropolitan areas. The state is dominated by the two urban/inner suburban regions of Washington, D.C. and Baltimore. In addition, many jobs are directly or indirectly dependent upon the federal government. As a result, Baltimore, Montgomery County and Prince George's County often decide statewide elections. This is balanced by lesser populated areas on the Eastern Shore, Western Maryland, and outer suburbs that tend to support Republicans, even though seven of nine Shore counties have Democrat-majority voter rolls.

Maryland has supported the Democrat candidate in the last four presidential elections, and by an average of 15.4%. In 1980, it was one of just 6 states to vote for Jimmy Carter. Maryland is often among the Democrat nominees' best states. In 1992, Bill Clinton fared better in Maryland than any other state except his home state of Arkansas. In 1996, Maryland was Clinton's 6th best, in 2000 Maryland ranked 4th for Gore and in 2004 John Kerry showed his 5th best performance in Maryland.

While Maryland is a Democratic party stronghold, perhaps its best known political figure is a Republican--former Governor Spiro Agnew, who served as United States Vice President under Richard Nixon. He was Vice President from 1969 to 1973, when he resigned in the aftermath of revelations that he had taken bribes while he was Governor of Maryland.

Both Maryland Senators and six of its eight Representatives in Congress are Democrats, and Democrats hold super-majorities in the state Senate and House of Delegates. John Kerry easily won the state's 10 electoral votes in 2004 by a margin of 13 percentage points with 55.9% of the vote. However, presidential election years are not deeply contested as national party resources are spent mostly in swing states, and turnout and interest is frequently relatively low.

Maryland's economic activity is strongly concentrated in the tertiary service sector, and this sector, in turn, is strongly influenced by location. One major service activity is transportation, centered around the Port of Baltimore and its related rail and trucking access. The port ranked 10th in the U.S. by tonnage in 2002 (Source: U.S. Corps of Engineers, "Waterborn Commerce Statistics"). Although the port handles a wide variety of products, the most typical imports are raw materials and bulk commodities, such as iron ore, petroleum, sugar, and fertilizers, often distributed to the relatively close manufacturing centers of the inland Midwest via good overland transportation. The port also receives several different brands of imported motor vehicles.

A second service activity takes advantage of the close location of the center of government in Washington, D.C. and emphasizes technical and administrative tasks for the defense/aerospace industry and bio-research laboratories, as well as staffing of satellite government headquarters in the suburban or exurban Baltimore/Washington area. In addition many educational and medical research institutions are located in the state. In fact, the various components of Johns Hopkins University and its medical research facilities are now the largest single employer in the Baltimore area. Altogether, white collar technical and administrative workers comprise 25% of Maryland's labor force, one of the highest state percentages in the country.

Many Federal government agencies are located in Maryland.