Hudson County is a densely populated county in the U.S. state of New Jersey. It lies west of the lower Hudson River, which was named for Henry Hudson, the sea captain who explored the area in 1609. Part of New Jersey's Gateway Region in the New York metropolitan area, the county's county seat and largest city is Jersey City, with a population of 292,449 enumerated at the 2020 U.S. Census. As of the 2020 United States Census, Hudson County was the fastest-growing county in New Jersey compared to 2010; the county reached total poulation of 724,854 as of 2020, representing an increase of 90,588 residents (14.3%) over the population of 634,266 counted in the 2010 U.S. Census, making Hudson the state's fourth-most populous county. Home to 15,693 residents per square mile (6,130/km2) in 2020, covering only 46.19 square miles of land, Hudson County is New Jersey's geographically smallest and most densely populated county as well. Its 2010 population in turn was an increase of 25,291 (4.2%) from the 2000 U.S. Census, when the county's population was established to be 608,975, Hudson Coutny shares extensive mass transit connections with Manhattan, located across the Hudson River, as well as with most of Northern and Central New Jersey.

New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware River and Pennsylvania; on the southwest by Delaware Bay and the state of Delaware. At 7,354 square miles (19,050 km2), New Jersey is the fifth-smallest state based on land area, but with close to 9.3 million residents, is the 11th-most populous and the most densely populated. New Jersey's state capital is Trenton, while the state's most populous city is Newark. With the sole exception of Warren County, all counties in the state lie within the combined statistical areas of New York City or Philadelphia; consequently, the state's largest metropolitan area falls within Greater New York. New Jersey was first inhabited by Native Americans for at least 2,800 years, with the Lenape being the dominant group when Europeans arrived in the early 17th century. Dutch and the Swedish colonists founded the first European settlements in the state. The English later seized control of the region and established the Province of New Jersey, after the largest of the Channel Islands, Jersey. The colony's fertile lands and relative religious tolerance drew a large and diverse population. New Jersey was among the Thirteen Colonies that opposed Great Britain, hosting numerous pivotal battles and military commands in the American Revolutionary War. The state remained in the Union during the U.S. Civil War, and thereafter became a major center of manufacturing and immigration; it helped drive the nation's Industrial Revolution, and became the site of numerous technological and commercial innovations into the mid 20th century. New Jersey's central location in the Northeast megalopolis fueled its rapid growth and suburbanization in the second half of the 20th century. At the turn of the 21st century, its economy increasingly diversified, with major sectors including biotechnology, pharmaceuticals, specialized agriculture, and informational technology. New Jersey remains a major destination for immigrants, with one of the most multicultural populations in the U.S. Echoing historic trends, the state has increasingly re-urbanized, with growth in the cities outpacing the suburbs since 2008. New Jersey is one of the wealthiest states in the U.S., with the second highest median household income in 2017. Almost one-tenth of all households, or over 323,000 of 3.3 million, are millionaires, the highest rate per capita in the country. New Jersey's public school system consistently ranks at or among the top of all U.S. states.

The Bronx () is a borough of New York City, coextensive with Bronx County, in the U.S. state of New York. It is south of Westchester County; north and east of the New York City borough of Manhattan, across the Harlem River; and north of the New York City borough of Queens, across the East River. The Bronx has a land area of 42 square miles (109 km2) and a population of 1,472,654 in the 2020 census. If each borough were ranked as a city, the Bronx would rank as the ninth-most-populous in the U.S. Of the five boroughs, it has the fourth-largest area, fourth-highest population, and third-highest population density. It is the only borough of New York City not primarily on an island. The Bronx is divided by the Bronx River into a hillier section in the west, and a flatter eastern section. East and west street names are divided by Jerome Avenue. The West Bronx was annexed to New York City in 1874, and the areas east of the Bronx River in 1895. Bronx County was separated from New York County in 1914. About a quarter of the Bronx's area is open space, including Woodlawn Cemetery, Van Cortlandt Park, Pelham Bay Park, the New York Botanical Garden, and the Bronx Zoo in the borough's north and center. The Thain Family Forest at the New York Botanical Garden is thousands of years old; it is New York City's largest remaining tract of the original forest that once covered the area of the city. These open spaces are situated primarily on land deliberately reserved in the late 19th century as urban development progressed north and east from Manhattan. The word "Bronx" originated with Faroese-born (or Swedish-born) Jonas Bronck, who established the first settlement in the area as part of the New Netherland colony in 1639. The native Lenape were displaced after 1643 by European settlers. In the 19th and 20th centuries, the Bronx received many immigrant and migrant groups as it was transformed into an urban community, first from various European countries (particularly Ireland, Germany, Italy and Eastern Europe) and later from the Caribbean region (particularly Puerto Rico, Haiti, Jamaica, and the Dominican Republic), as well as African American migrants from the southern United States. This cultural mix has made the Bronx a wellspring of Latin music, hip hop and rap. The Bronx contains the poorest congressional district in the United States, the 15th. There are, however, some upper-income, as well as middle-income neighborhoods such as Riverdale, Fieldston, Spuyten Duyvil, Schuylerville, Pelham Bay, Pelham Gardens, Morris Park, and Country Club. Parts of the Bronx saw a decline in population, livable housing, and quality of life in the late 1960s, throughout the 1970s and 1980s, and into the early 1990s, culminating in a wave of arson in the late 1970s. The South Bronx, in particular, experienced severe urban decay. The borough experienced some redevelopment starting in the late 1990s, with concomitant gentrification following.