Christopher Columbus discovered the American continent in 1492. He was sailing west from Spain in order to find a new route to India. He carried a passport which authorized his journey in the name of the Spanish monarchs.
So when he discovered American continent, the Spanish were the first to know about this. This is why they were the first to launch exploration and colonization attempts of the continent. Their attempts were immensely successful and they were able to carve out a large colonial empire on the continent.
The Spanish possessions in the Americas were included in the Spanish Viceroyalty of New Spain. In the Americas, this comprised of a vast land area that stretched across almost all of Central America and large portions of North America.
In the North America, Spanish colonies comprised of many modern-day states of United States. These included California, Colorado, Nevada, Utah, Arizona, Texas, Oregon, New Mexico, Washington and Florida. Spanish colonies also included parts of the modern-day states of Louisiana, Kansas, Wyoming, Oklahoma, Idaho and Montana.
When Spanish first arrived on the American continent, they met with the Native Americans. At the time, the Native Americans knew little to nothing about the Europeans.
In Central America, conquistadors or Spanish adventurers with mercenary soldiers attacked and conquered the Native American Aztec and Inca empires.
The conquest of these empires brought an exceptional amount of wealth and resources to Spain, effectively making it one of the most powerful nations in Europe. These conquests which began as early as 1521 also paved the way for the expansion of Spanish control towards North America.
The rulers of the Spanish empire at the time were known as Catholic monarchs. This was because they strongly believed in Catholic Christianity and supported the Catholic Church. They also believed they had a religious mission of spreading Christianity throughout the world.
This is why when Spanish conquistadors established Spanish colonies in the Americas, they also started Christianizing the native population. They forced many Native Americans to convert to Christianity. They also enslaved many of them to work on their ranches or farms.
In 1513, Spanish Florida was established as one of the earliest Spanish colonies in North America. However, it remained a colony of little importance for Spain.
Along the coast, the Spanish established St. Augustine which became an important port for ships. Florida remained mostly in Spanish possession until Spain ceded it to United States in 1519.
The Louisiana Territory was an important part of the French colonies in North America. In 1762, France ceded the territory to Spain. During Spanish control, the population of Louisiana rapidly expanded. In 1802, Spain was forced by Napoleon Bonaparte to recede the territory which soon became a part of USA.
When United States came into being, Spanish still had colonial control over portions of southern and eastern territories. Some of these were given to USA through treaties. Others, such as Texas, fought for their freedom from Spanish colonial rule and chose to become a part of USA.