Over 500 years ago, tribes from the south practiced horticulture near present-day Lockport.
The spread of maize-growing agriculture on the central and northern great plains between 400 CE and 800 CE encouraged the growth of concentrated settlements.
Better mastery of the food supply by the peoples living there contributed to population growth. Long distance trade also thrived.
The biggest city to be built was Cahokia in modern-day Illinois. At one point, about 30 000 people lived there.
A number of things probably contributed to the collapse of Cahokia and related regions. Drought, flooding, warfare, and unwise use of local resources have all been proposed as factors. Whatever the case, by 1350 CE, Cahokia was gone, and its people dispersed.
Some of those who moved away from the old centers eventually made their way north. A few came to present day Manitoba.
Rising temperatures during the middle ages helped extend the growing line north of Lockport, making agriculture possible in the area. Additionally, floods deposited soil that made the ground more favourable for farming.
The medieval warm period lasted from the mid-10th to the mid-13th centuries. Following it came the little ice age, during which time temperatures became progressively colder.
In Norway, nearly one third of farms that had thrived during the warm centuries had to be abandoned. Agriculture faced a major setback all over northern Europe.
It was apparently just after the beginning of the dip in temperatures that the Lockport fields were ploughed. Whether due to the continually worsening climate or to other factors, the people who lived here abandoned their operation by the mid-15th century.