The first city in the Northeastern United States is Boston, Massachusetts. This city holds the distinction of being the oldest city in the region, having been founded in 1630 by Puritan settlers. Boston's historical significance and its role in the American Revolution have cemented its place as the first city in the Northeast.

Boston's status as the first city in the Northeast is supported by various historical records and data. The city's founding date, 1630, predates the establishment of other prominent Northeastern cities such as New York City (1685) and Philadelphia (1682). This chronological precedence is well-documented in historical texts and scholarly research. Additionally, Boston's role as a hub of colonial activity and its pivotal role in the American Revolution further solidify its position as the first city in the Northeast.

The historical significance of Boston is not only reflected in its founding date but also in its cultural and political contributions. The city is renowned for its rich history, including the Boston Tea Party, the Siege of Boston, and the Declaration of Independence. These events, among others, have shaped the course of American history and have made Boston a symbol of American independence and freedom.

Furthermore, Boston's geographical location in the Northeast also supports its claim as the first city in the region. The Northeastern United States is generally defined as the region that includes the states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut. Boston, being located in Massachusetts, is at the geographical center of this region, making it a logical candidate for the first city.

In conclusion, Boston, Massachusetts, is the first city in the Northeastern United States, primarily due to its early founding date of 1630 and its significant historical and cultural contributions. The city's role in American history and its geographical position in the Northeast further reinforce its status as the first city in the region.