The griffin land started out as a frozen Ice Age land populated by Windigoes. The griffins' greed and lust for gold made the cold even worse. But they actually didn't need to change in order to get rid of them. The Windigoes left on their own when they discovered that there was much stronger arguing in the pony lands. With no more Windigoes freezing their home land, the griffins started to become civilized creatures, forming their own rich government ruled by a single king. However, the monarchy didn't last very long when it turned into a land ruled by multiple kings and queens since wars started to erupt for the control of the kingdom. Thus the kingdom was divided up until tension between them was settled. Unfortunately, it never settled since the griffins were still greedy and willing to rob riches from each others' neighboring kingdoms.
This conflict had lasted for over 50 years, yet everything changed when another greedy race came into the picture: the Arimaspi people from the mountains across the griffin kingdoms. Beings twice as greedy as dragons, the Arimaspi had began committing mass robberies of the gold stashes, setting off an even worse conflict for the griffins. Thus the kingdoms were forced to work together to stop the Arimaspi from their gold thefts. But conflicts escalated because of this, and before they knew it, these two races declared war on each other. Many colonies had to be created across Equestria to protect some of their gold stashes, including Griffonstone, which was also unsafe.
Things got worse for the griffins when the Arimaspi became steadfast allies to Pitch Black during the Great Fear War, which would lead to the forming of the Unity that would try to establish peace against other races, with little success. When the war ended, the Arimaspi were left with no protection from a griffin invasion that would steal back all the wealth they gained from Pitch Black's assistance. While this invasion lead to the death of one of the kings, the Arimaspi were angry and initiated a counter-invasion and began killing hundreds of griffins. When the kings had finally had enough, they called the Celestial sisters to put a stop to this conflict. Thus the Arimaspi people were banished back to their territory, and were threatened with a penalty for returning.
Angry that the Celestial sisters interrupted their revenge scheme, the Arimaspi began an invasion on several other griffin colonies across Equestria, even having to resort to killing other creatures including ponies if they had to. One of these attacks included that on Griffonstone where an extremely daring Arimaspi king would steal the Isle of Boreas and die trying to get away with it, left with the success of his mission as the colony went into ruins. The same thing occurred for several other griffin colonies and Celestia and Luna were powerless to stop them because of the fact that it would violate their obligations to the Unity, even when the Arimasi were not even part of it for obvious reasons, which is one of the many reasons why the Des Clan was considered heroes, killing the Arimaspi who murdered any pony who stood in the way of their goals.
It didn't take until a Slavery Foundation that the Arimaspi were stopped for good. The griffins have decided that the Arimaspi have grown too mistrustful of redemption, and started putting them in slavery camps. This eventually lead to the Arimaspi retreating to another land where they would no longer have to put up with the cruelty of the griffins. Though while slavery of the Arimaspi were no longer an option, the griffins decided that ponies were a proper replacement. This ended up partnering up with other mythic beasts, including Dragons, Hobgoblins and Centaurs, cause things weren't exactly settled with the ponies yet. While the newly renamed "Pony Slavery Foundation" was ironicly benvolent in economic terms, it obviously wasn't appresiated by ponies because of the amoral lack of caring to who the ponies end up with, even to those that plan to do the "other kind of slavery", and often unclean conditions the ponies were kept in. Many ponies have began suffering and getting abused to do as the griffins said. However, Celestia finally had enough and with help of the mutual feelinsg of all the mythic kings, including the griffin kings, they have issued the disbandment of the foundation, and through it lead to a slight ecomonic crisis, it was considered a short-term loss to bettering relations between ponies and mythic beings, if though not nessersarly over-night, leaving some of the descendants to found the Griffin Mafia to try and take advantage of the land's lack of a central king. This Mafia still remains alive today, yet several others are taking advantage of the same thing. But even they are not even the true biggest problem, cause even the powerful griffin mafia is easily over-shadowed by a powerful magi-griffin Queen named Queen Magi, who defelupted a serious taste for power all for the sake of making sure her son is well provided for should she be one day gone. But Celestia, Luna, and the current griffin kings have a plan to fix this in the form of King Cedric, the most wise and benevolent of all the kings in Griffinmainia. They still haven't fixed this problem as of yet, but it will be fixed as soon as certain problems are corrected.
The architecture of Griffinmainia is just treehouses resting on trees ranging on size. Griffins are known to be semi-arboreal due to their bird-like accommodations, and they build their treehouses as high as they can go, not just on trees, but high geological sites such as mesas, cliffs, and mountains. Though the countries were mainly restricted to their main territory called Hyperboreas, and outside colonies on the land were rare. Though the old homeland of the Arimaspi, Scythius just across the Riphea Mountains was made a forbidden zone since dangerous predators that were either domesticated by the Arimaspi or just indigenous monsters were taking up the ruins of their villages, and were instinctively hostile to griffins.
Like their colonies, the griffins have kings and queens that take up large arboreal tree castles. The Hyperboreas lands are split up in several kingdoms as the result of the first inter-kingdom wars long ago before the wars against the Arimaspi. And since griffins are considered the guardians of gold, there are massive stashes of wealth in these kingdoms that are hidden in varying locations. As a result, the griffins are the richest beings in Equestria. They are able to afford anything they desire, though this belief has left the species to have a cheapskate following, even going as far as to charge for anything no matter how immoral it was.
Despite the fact that these creatures have a bit of a controversial cheapness, some are still moral. Others like the Griffin Mafia are not just greedy for money, but for the speculative position of becoming the top ruler of the land. King Cedric is well aware of this problem, and has assisted Celestia and Luna to deal with the problems. The griffins are also more than just hereditarily greedy. They are also good cooks since they make good scones, bread, and seeds. They are also pretty good gamblers, and all know how to play good card games, and are extremely athletic since all griffins had to learn to fight against the Arimaspi long ago, and made it into a clever tradition to build up skills.