Short answers, pulled from the story.
Cahokia reached its peak population around the year 1050. This settlement housed more than 10,000 people, a size unmatched by any city in the United States until the early 1800s.
Monks Mound is the largest prehistoric earthen construction in the Americas. This massive earthen pyramid stands 100 feet tall and covers 14 acres at its base.
The decline of Cahokia began in the mid-14th century due to climate change and environmental degradation. The Little Ice Age brought cooler temperatures and reduced rainfall that severely impacted maize agriculture, leading to the city's abandonment around 1350.
The main mythological figures are the Birdman and the Serpent. The Birdman is a human figure with bird-like features often holding a mace or severed head, while the Serpent is a long, sinuous creature associated with the underworld and waters.
The first significant contact occurred with the expedition of Hernando de Soto in 1539. This journey traversed the heart of the Mississippian world from Florida to the Mississippi River and introduced diseases that caused massive population declines.