The vast majority of people here illegally overstayed visas, not by illegal crossings. The wall is a solution looking for a problem. You might as well design a new power cord for a brick phone. The problem with sanctuary cities is easy to solve. Make being illegal a felony instead of a civic matter, then the feds will be responsible for paying to keep and house those that are caught instead of dumping the bills on local police forces who can't legally hold them anyway.