When was the concept of the "border wall" between the United States and Mexico first proposed?
The current American president Donald Trump has become notorious for (among other things) championing the idea to build a 18+ foot concrete wall across the entire US/Mexican border. Where did this concept originally come from? A news article I read some time ago (which frustratingly I can't find right now) dating back to Bush Sr.'s term commented on the development of some sort of river extension project which would 'incidentally' serve as a moat and garnered a protest from the Mexican government at the time, so developing a large barrier is not an idea unique to the 2016 political landscape, but I'm curious if that project in the '90s was the first real attempt in this direction. The earliest date that any massive building project somewhat similar in scale to Donald Trump's wall, whether a wall, ditch or moat, was proposed would be sufficient to answer this question. For "bonus points", if this idea came up regularly in US history, when did it first become politically or socially unpopular (rather than being merely viewed as impractical)?