What is the flag union?

The "union" is also known as the "canton" in flag terms. When looking at the flag, it is the upper left corner of the flag, the position of honor. This is also the "flag's right" corner from the flag's perspective looking at you, the viewer. The term "union" comes from the Second Continental Congress resolution on June 14th 1777 that defined the first flag of the United States of America: "Resolved, That the flag of the United States be thirteen stripes, alternate red and white; that the union be thirteen stars, white in a blue field, representing a new Constellation."