What does the rectangle on the US flag mean?

What was a form of labor that had a finite period of time and mainy used young white males? Leading to the Civil war the south had an economy based on agriculture and slave labor while the north had an economy based on what? Who found the Native American first? What did children take to school for lunch in early 1900s? What time period of history did Mae jemison live? What are some of the native delicacies made from Galapong? What is the value of a 1957 US gold certificate? What was the major reason for sectional tension over the building of the transcontinental railroad? What is the oldest US quarter? What is Abraham Lincoln's phone number? 1943 liberty dime worth? What are the lessons in bicentennial man? What lesson was learned from Bacon's Rebellion? What was life like in the 1820s? What happened because of the red scare? Why was the expansion of slavery a cause of the civil war? How were the french colonial attempts different from the Spanish colonial attempts? Whose face is on the 1972 one dollar coin in the US? Can Hillary be a boys name? Was the us considered the union?