The locations of Federal Reserve District boundaries, and of the Banks within the Districts, were determined mostly by the geographic distribution of the U.S. population at the time the Federal Reserve System was created (1913), to accommodate local needs.
Mr Trump claims the total cost of the wall will be $10bn (Â£7.5bn) to $12bn. But estimates from fact checkers and engineers seem to be universally higher. Senate Majority Leader Mitch McConnell estimated it will cost between $12-15bn, as he addressed reporters at a Republican conference in Philadelphia.
According to a Government Accountability Office 2009 report, the cost to build 1 mile of fencing at the border averaged between $2.8 million and $3.9 million. But that figure may be low relative to costs for future sections of the wall.