the atlantic
Two
Waterways can be hard to get across so surrounding or going around it would be a natrual boundary. Countries and states on North America are mostly separated by artificial boundaries. The artificial boundaries are called boarders. All of North America is surrounded by water. The water is a natural boundary of the entire continent.
The City of Chicago is located within the boundaries of Cook and DuPage Counties which are located within the boundaries of the State of Illinois which is located within the boundaries of the United States of America which is located within the boundaries of the continent of North America.
North America and South America have edges that are not all plate boundaries. The boundary between North and South America is known as the Central American Subduction Zone, where the Cocos Plate is subducting beneath the Caribbean Plate.
The Mississippi and the Missouri rivers are on the continent of North America.
North America is large enough for the US to fit within its boundaries.
The largest desert in North America is the Great Basin Desert followed closely by the Chihuahuan Desert. It depends upon where the 'experts' draw the boundaries.
The San Andreas Fault zone of western North America.
The North Pacific Ocean is to the West of North America. The boundaries are: North-Artic Ocean South-Southern Ocean West-Americas East-Australia and Asia
oregon
There are a number of natural boundaries of North Korea. These boundaries include the Korean Bay to the west, the Sea of Japan to the east, and the Duman River to the north.
It happened in the United States, both the North and the South, but it was more prevalent in the South. Unfortunately, it is still happening by default because school district boundaries reflect the socioeconomic and often racial boundaries in our communities.