During the 1850s, there were a number of filibustering expeditions aimed at conquering portions of Central America, South America, and the Caribbean. Most of these excursions were usually organized by pro-slavery Southerners from the southern US, and intended to gain more land to spread slavery into.
The most notable of these filibustering organizations were the Knights of the Golden Circle (KGC). The KGC was established around 1855 by an Indiana physician named George Bickley, and it was very active in the years directly preceding the Civil War (1861).
Bickley’s goal was to essentially create a Caribbean empire that could, one day, be so powerful that it would rival the grandeur of Ancient Rome. His plan called for the secession of the southern states along the Gulf of Mexico (Texas, Florida, Alabama, Mississippi, Louisiana, and even Georgia) and then to raise an army and conquer Mexico, Central America, the northern countries of South America, and the Caribbean islands.
The lands that Bickley wanted to conquer were some of the richest agricultural nations in the world. All of the most profitable raw goods of the day (sugar, cotton, beef, tobacco, fish, etc.) grew or was raised in this “Golden Circle” area around the Caribbean.
Although extremely ambiguous, Bickley’s ideals found massive support in the southern and mid-western states. By the late 1850s, the Knights of the Golden Circle was a fully functioning secret society of filibusters and slavery expansionists.
The KGC gained the most support in Texas. So, around 1858, Bickley moved the headquarters of the organization into eastern Texas. In addition to the growing numbers of volunteer soldiers that the KGC was amassing, Bickley also got promised military aid from underground officials in Mexico who were plotting an overthrow of the current presiding party in Mexico City.
At one point in time, around 1858, it appeared that everything was a go for the KGC’s invasion plans. Around 500 KGC soldiers gathered at a location in Encinal County, Texas (which no longer exists today) and were awaiting orders to proceed across the Rio Grande. The Galveston newspaper even reported the growing number of KGC troopers...although the newspaper really mocked them more than supported them.
After about a week of camping, Bickley ordered the forces in Encinal County to return to their homes because the underground Mexican revolutionaries had pulled out of the deal. They were planning to re-assembly at a later date, but never did.
Members of the KGC actually played a major role in Texas once the state seceded in 1861. Detachments of Knights were sent to help secure the western Federal forts, and there was even a large company of KGC soldiers at San Antonio when the Federal command of Texas was surrendered to the South.
The organization died with the Civil War. Members were sent everywhere, KGC regiments were divided up and assimilated into the Confederate military forces, and Bickley was even thrown in prison for treason in New England.
After the war, there are stories about the KGC hiding treasures and other stuff all across the country. According to folklore, they were preparing for a second Civil War right after the first one ended.
There’s very little truth to the treasure stories of the KGC, even though there is evidence of some sort of criminal organization operating under the name “Knights of the Golden Circle” in the late 1800s. But, the KGC was popular for only a few years before it finally played itself out at the onset of the Civil War.
For references, check out:
“Blood & Treasure” “An Authentic Exposition of the KGC” Numerous historical essays on the Knights that have been published in academic societies like the Southwestern Historical Quarterly. “Order of the Sons of Liberty” And, numerous newspaper outlets of the time.
There's room for more discussion on this, but the faq has a very good subsection on this topic.
See especially this great answer by u/legendarytubahero on colonial organisation and how it led to post-independence national states rather than a union of states.
And this post by u/ThucydidesWasAwesome on the fascinating and failed attempt by Bolívar to form a confederated state during the "Congreso Anfictiónico de Panamá" of 1826; and on a second equally failed congress in Tacubayá, Mexico in 1828.
I'll add a brief overview of reasons that hindered such attempts at union building:
The different regions of Spanish America were organized on different levels. The largest units were the four viceroyalties of New Spain (mostly modern Mexico, the Western U.S., and Central America); New Granada (mostly modern Colombia, Ecuador, Panama, and Venezuela); Peru (mostly modern Peru); and Rio de la Plata (mostly modern Argentina, Bolivia, Paraguay and Uruguay). Below the viceroyalties were seperate Captaincy Generals: Most interestingly for us here Chile, Guatemala, and Venezuela. At an even lower level there were the audiencias, which can be described as local administration.
During colonial times, quite early on the Spanish Crown ruled that the Viceroyalties could not trade between them, and that all trade should go through Sevilla/Cádiz. While there were exceptions to this rule, esp. following the Bourbon Reforms, it nonetheless meant that there was comparatively little communication and exchange between the 4 viceroyalties. This of course also had to do with the huge distances lying e.g. between central America and southern South America. This was one major influence on the breaking apart of the former viceroyalties into independent countires in the early 19th century. They were then quickly further fragmented, sometimes along the Capatincy Generals (in the regions mentioned above) and sometimes along audiencias (in the Rio de la Plata and the former New Granada).
Adding to these more general socio-political factors is the influence of the elites of newly independent Spanish America. The creole elites held far from unitary views on how to organize following indepence. This can already be seen in the short meeting in 1822 between probably the two most famous pro-independence generals during the wars - Simon Bolívar and José de San Martín. While the latter tended towards some inclusion of royalty in American political systems, Bolívar's views shuttled between republicanism, to an inclusion of some leader figure in his later life. In any case the meeting ended in disachord and with San Martín resigning in favor of Bolívar.
Moving beyond such individual leaders' viewpoints, the development of a "creole patriotism" during the colony is also often mentioned in this context - with creoles meaning people of European origin born in the Americas. Over time their grievances over being left off the most important governance posts, which were only open to Europeans, influenced a form of patriotism. Benedict Anderson famously saw this developing into an early nationalism with Spanish American independence, in some ways predating forms of nationlism in many European regions.
Anyways, such patriotism was stronger developed in certrain regions like Mexico/New Spain or Peru, where it can be traced already ot the 17th century. But other regions like Argentinia also developed distinct forms of patriotism during the 18th and 19th centuries. So that we can see here another factor of cohesion in these regions, which would have made it more difficult to arrange a union covering all or parts of Spanish America. Last but not least, the division of South America into its modern day nations was a gradual process, with border conflicts - another colonial heritage - lasting well into the early 20th century.
a repost from my own post here
Benedict Anderson in his Imagined Communities puts forward a theory for the breakup of the former Spanish colonies.
Creoles, Spanish born in the new world, functionaries basically only served in Mexico or their 'native' territory. For example an Argentinean bureaucrat could work in Argentina or Mexico but not Peru or Chile.
The different territories were very far apart, making travel difficult and time consuming.
Newspapers reported on events in such a way that local events were seen as part of events in that territory, which became an imagined community of similar people, while events in other regions were seen as similar, but not the same.
This is true today, think about how Canadians and Americans react to something happening in Windsor OR Detroit involving people they have never met.
Thus the elites were not gaining the idea of a United States of South America.
Anderson states that:
the 'failure' of the Spanish-American experience to generate permanent Spanish-American-wide nationalism reflects both the general level of development of capitalism and technology ... [and their] backwardness ... in relation to the administrative stretch of the empire. (pp63)
I added the [and their]