Treaty of Guadalupe Hidalgo in the context of "Red River of the South"

The San Francisco Bay Area, commonly known as the Bay Area, is a region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose. The Association of Bay Area Governments defines the Bay Area as including the nine counties that border the estuaries of San Francisco Bay, San Pablo Bay, and Suisun Bay: Alameda, Contra Costa, Marin, Napa, San Mateo, Santa Clara, Solano, Sonoma, and San Francisco. Other definitions may be either smaller or larger, and may include neighboring counties which are not officially part of the San Francisco Bay Area, such as the Central Coast counties of Santa Cruz, San Benito, and Monterey, or the Central Valley counties of San Joaquin, Merced, and Stanislaus. The Bay Area is known for its natural beauty, prominent universities, technology companies, and affluence. The Bay Area contains many cities, towns, airports, and associated regional, state, and national parks, connected by a complex multimodal transportation network.

The earliest archaeological evidence of human settlements in the Bay Area dates back to 8000–10,000 BC. The oral tradition of the Ohlone and Miwok people suggests they have been living in the Bay Area for several hundreds if not thousands of years. The Spanish empire claimed the area beginning in the early period of Spanish colonization of the Americas. The earliest Spanish exploration of the Bay Area took place in 1769. The Mexican government controlled the area from 1821 until the 1848 Treaty of Guadalupe Hidalgo. Also in 1848, James W. Marshall discovered gold in nearby mountains, resulting in explosive immigration to the area and the precipitous decline of the Native population. The California gold rush brought rapid growth to San Francisco. California was admitted as the 31st state in 1850. A major earthquake and fire leveled much of San Francisco in 1906. During World War II, the Bay Area played a major role in America's war effort in the Asiatic-Pacific Theater, with the San Francisco Port of Embarkation, of which Fort Mason was one of 14 installations and location of the headquarters, acting as a primary embarkation point for American forces. Since then, the Bay Area has experienced numerous political, cultural, and artistic movements, developing unique local genres in music and art and establishing itself as a hotbed of progressive politics. The postwar Bay Area saw large growth in the financial and technology industries, creating an economy with a gross domestic product of over $700 billion. In 2018 it was home to the third-highest concentration of Fortune 500 companies in the United States.

The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that includes Arizona and New Mexico, along with adjacent portions of California, Colorado, Nevada, Oklahoma, Texas, and Utah. The largest cities by metropolitan area are Phoenix, Las Vegas, El Paso, Albuquerque, and Tucson. Before 1848, in the historical region of Santa Fe de Nuevo México as well as parts of Alta California and Coahuila y Tejas, settlement was almost non-existent outside of New Mexico's pueblos and Spanish or Mexican municipalities. Much of the area had been a part of New Spain and Mexico until the United States acquired the area through the Treaty of Guadalupe Hidalgo in 1848 and the smaller Gadsden Purchase in 1854.

While the region's boundaries are not officially defined, there have been attempts to do so. One such definition is from the Mojave Desert in California in the west (117° west longitude) to Carlsbad, New Mexico, in the east (104° west longitude); another says that it extends from the Mexico–United States border in the south to the southern areas of Colorado, Utah, and Nevada in the north (39° north latitude). In another definition, the core Southwestern U.S. includes only the states of Arizona and New Mexico; others focus on the land within the old Spanish and Mexican borders of the Nuevo México Province or the later American New Mexico Territory.

The land which became the United States was inhabited by Native Americans for tens of thousands of years; their descendants include but may not be limited to 574 federally recognized tribes. The history of the present-day United States began in 1607 with the establishment of Jamestown in modern-day Virginia by settlers who arrived from the Kingdom of England, and the landing of the Mayflower by English pilgrims to Plymouth in 1620. In the late 15th century, European colonization began and largely decimated Indigenous societies through wars and epidemics. By the 1760s, the Thirteen Colonies, then part of British America and the Kingdom of Great Britain, were established. The Southern Colonies built an agricultural system on slave labor and enslaving millions from Africa. After the British victory over the Kingdom of France in the French and Indian Wars, Parliament imposed a series of taxes and issued the Intolerable Acts on the colonies in 1773, which were designed to end self-governance. Tensions between the colonies and British authorities subsequently intensified, leading to the Revolutionary War, which commenced with the Battles of Lexington and Concord on April 19, 1775. In June 1775, the Second Continental Congress established the Continental Army and unanimously selected George Washington as its commander-in-chief. The following year, on July 4, 1776, the Second Continental Congress unanimously declared its independence, issuing the Declaration of Independence. On September 3, 1783, in the Treaty of Paris, the British acknowledged the independence and sovereignty of the Thirteen Colonies, leading to the establishment of the United States. On September 17, 1787, the U.S. Constitution was signed by a majority of delegates, and was later ratified by the Thirteen Colonies, leading to the first modern U.S. government.

In the 1788-89 presidential election, Washington was elected the nation's first U.S. president. Along with his Treasury Secretary, Alexander Hamilton, Washington sought to create a relatively stronger central government than that favored by other founders, including Thomas Jefferson and James Madison. On March 4, 1789, the new nation debated, adopted, and ratified the U.S. Constitution, which is now the oldest and longest-standing written and codified national constitution in the world. In 1791, a Bill of Rights was added to guarantee inalienable rights. In 1803, Jefferson, then serving as the nation's third president, negotiated the Louisiana Purchase, which doubled the size of the country. Encouraged by available, inexpensive land, and the notion of manifest destiny, the country underwent westward expansion in a project of settler colonialism marked by a series of conflicts with the continent's indigenous inhabitants. The most notable advocate of manifest destiny was President James K. Polk, who annexed Texas in 1845, and declared war on Mexico the next year. An overwhelming U.S. victory in the Mexican-American War led to the Treaty of Guadalupe Hidalgo in 1848, where the U.S. acquired much of the American Southwest from Mexico. Whether or not slavery should be legal in the expanded territories was an issue of national contention, and led to increasing tensions over slavery.

Colorado is a landlocked state in the Western United States. It is one of the Mountain states, and Southwestern region of the United States, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas to the east, and Oklahoma to the southeast. Colorado is noted for its landscape of mountains, forests, high plains, mesas, canyons, plateaus, rivers, and desert lands. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains. Colorado is the eighth-largest U.S. state by area and the 21st by population. The United States Census Bureau estimated the population of Colorado to be 5,957,493 as of July 1, 2024, a 3.2% increase from the 2020 United States census.

The region has been inhabited by Native Americans and their Paleo-Indian ancestors for at least 13,500 years and possibly much longer. The eastern edge of the Rocky Mountains was a major migration route for early peoples who spread throughout the Americas. In 1848, much of the Nuevo México region was annexed to the United States with the Treaty of Guadalupe Hidalgo. The Pike's Peak Gold Rush of 1858–1862 created an influx of settlers. On February 28, 1861, U.S. President James Buchanan signed an act creating the Territory of Colorado, and on August 1, 1876, President Ulysses S. Grant signed Proclamation 230, admitting Colorado to the Union as the 38th state. The Spanish adjective "colorado" means "colored red" or "ruddy". Colorado is nicknamed the "Centennial State" because it became a state 100 years (and four weeks) after the signing of the United States Declaration of Independence.

The Mexican Cession (Spanish: Cesión mexicana) is the territory that Mexico ceded to the United States in the Treaty of Guadalupe Hidalgo in 1848 after the Mexican–American War. It comprises the states of California, Texas, New Mexico, Utah, Nevada, and Arizona, and parts of Colorado, Oklahoma, Kansas, and Wyoming in the present-day Western United States. Consisting of roughly 529,000 square miles (1,370,000 km), not including Texas, the Mexican Cession was the third-largest acquisition of territory in U.S. history, surpassed only by the 827,000-square-mile (2,140,000 km) Louisiana Purchase of 1803 and the later 586,000-square-mile (1,520,000 km) Alaska Purchase from Russia in 1867.

Most of the ceded territory had not been claimed by the Republic of Texas following its de facto independence in the 1836 revolution. Texas had only claimed areas east of the Rio Grande. After annexation into the U.S. and admission as a state in 1845, Texas's southern and western boundaries with the Mexican state of Santa Fe de Nuevo México had not been defined by the U.S. Most of the ceded area was part of the Mexican province of Alta California (Upper California) while the southeastern strip east of the Rio Grande had been part of the state of Santa Fe de Nuevo México. Mexico had controlled the ceded territories with considerable local autonomy. After the Mexican War of Independence finished in 1821, the area had seen several revolts but the Mexican government sent few troops from central Mexico to suppress them. In 1846, U.S. President James K. Polk sent soldiers to occupy the disputed territory between the Nueces River and the Rio Grande, starting the Mexican–American War. At the war's outbreak, the U.S. conducted a naval landing on Mexico's northeastern coast on the Gulf of Mexico, and advanced into Nuevo México.

Santa Fe de Nuevo México (English: Holy Faith of New Mexico; shortened as Nuevo México or Nuevo Méjico, and translated as New Mexico in English) was a province of the Spanish Empire and New Spain, and later a territory of independent Mexico. The first capital was San Juan de los Caballeros from 1598 until 1610, and from 1610 onward the capital was La Villa Real de la Santa Fe de San Francisco de Asís.

The name of "New Mexico", the capital in Santa Fe, the gubernatorial office at the Palace of the Governors, vecino citizen-soldiers, and rule of law were retained as the New Mexico Territory and later state of New Mexico became part of the United States. The New Mexican citizenry, primarily consisting of Hispano, Pueblo, Navajo, Apache, and Comanche peoples, became citizens of the United States as a result of the Treaty of Guadalupe Hidalgo (1848).

Alta California (English: Upper California), also known as Nueva California (English: New California) among other names, was a province of New Spain formally established in 1804. Along with the Baja California peninsula, it had previously comprised the province of Las Californias, but was made a separate province in 1804 (named Nueva California). Following the Mexican War of Independence, it became a territory of Mexico in April 1822 and was renamed Alta California in 1824.

The territory included all of the present-day U.S. states of California, Nevada, and Utah, and parts of Arizona, Wyoming, and Colorado. The territory was re-combined with Baja California (as a single departamento) in Mexico's 1836 Siete Leyes (Seven Laws) constitutional reform, granting it more autonomy. That change was undone in 1846, but rendered moot by the outcome of the Mexican–American War in 1848, when most of the areas formerly comprising Alta California were ceded to the U.S. in the treaty which ended the war. In 1850, California joined the union as the 31st state.