Howard County is included in the Baltimore-Columbia-Towson, MD Metropolitan Statistical Area, which is also included in the Washington-Baltimore-Arlington, DC-MD-VA-WV-PA Combined Statistical Area. However, recent development in the south of the county has led to some realignment towards the Washington, D.C. media and employment markets. The county is home to Columbia, a major planned community of approximately 100,000 founded by developer James Rouse in 1967.
Howard County is frequently cited for its affluence, quality of life, and excellent schools. With an estimated median household income of $108,844 in 2012, Howard County had the second-highest median household income of any U.S. county in 2013. Many of the most affluent communities in the Baltimore-Washington Metropolitan Area, such as Clarksville, Dayton, Glenelg, Glenwood and West Friendship, are located along the Route 32 corridor in Howard County. The main population center of Columbia/Ellicott City was named second among Money magazine's 2010 survey of "America's Best Places to Live." Howard County's schools frequently rank first in Maryland as measured by standardized test scores and graduation rates.
The lands of prehistoric Howard County were populated by Native Americans. The Maryland Historical Trust has documented sites along the Patapsco, Patuxent, Middle and Little Patuxent River valleys. In 1652, the Susquehannock tribes signed a peace treaty with Maryland, giving up their provenance over the territory that is now Howard County. In 1800, the mean center of U.S. population as calculated by the US Census Bureau was found in what is now Howard County.
In 1838, Dr. William Watkins of Richland Manor proposed the "Howard District" of Anne Arundel County. After several adjournments, the area of western Anne Arundel County was designated the Howard District in 1839. The district had the same status as a county except that it was not separately represented in the Maryland General Assembly. In 1841, the county built its first courthouse in Ellicott City. At the January 1851 constitutional convention, Thomas Beale Dorsey submitted a petition led by James Sykes. A committee was formed with Dorsey, Bowie, Smith, Harbine and Ricaud. After several postponements, the district became erected officially as Howard County on March 7, 1851.
The plantations of modern Howard County used slave labor as early as 1690. At the time of the Underground Railroad, some Howard County residents assisted slaves who were escaping to freedom. This was particularly risky, as many prominent plantation families were confederate sympathizers during the civil war, contributing militiamen to the South to protect local interests. Maryland was exempt from the Emancipation Proclamation, later abolishing slavery in the update of the Maryland Constitution in November 1864.
By 1899, Howard County contained of dirt and of stone roads, including three paid turnpikes maintained by 118 men. Most traffic consisted of loads delivered to rail crossings. In 1909, County Commissioners Hess, Werner and O'Neil were charged with malfeasance regarding contract bids.
In 1918, a deadly flu pandemic swept the county starting with an early outbreak in Camp Meade in adjacent Anne Arundel County. The 1930s saw a shift from one-room schoolhouses to centralized schools with bus service. By 1939 wheat harvesting fell to just . The Federal Aid Highway Act of 1956 eventually led to the construction of Interstate 70 across northern Howard County and Interstate 95 across the eastern part of the county. The sparsely populated county hosted population centers in Ellicott City, Elkridge, Savage, North Laurel and Lisbon with W.R. Grace and Johns Hopkins Applied Physics Lab as the largest new employers. Residents elected officials that campaigned to keep the county rural while planners prepared public works to support a quarter million residents by the year 2000. Race relations and desegregation became major issues of the time.
From 1963 to 1966 the Rouse Company bought of land and rezoned it for the Columbia Development. In 1972, the Marriott company proposed to build a regional theme park on Rouse-owned land but was denied zoning.
The county has a number of properties on the National Register of Historic Places.