Great Wall of China 14-17 century AD
Siegfried Line/Westwall 1917
Maginot Line 1932
A further list of walls here https://en.m.wikipedia.org/wiki/List_of_walls
All built to keep out "others". Is that who we are? America, where our motto has been
"Give me your tired, your poor,
Your huddled masses yearning to breathe free."
Let us not build walls of exclusion. Build roads to compromise. Let us not build walls to divide. Build roads to unite.