Whether through actual skill or luck, by the time he was 30, MacGregor became General of Division in the Army of Venezuela and New Granada. Then, he got to marry another rich heiress, this one a cousin to Simon Bolivar himself. If we managed to bullshit our way through life as much as MacGregor at this point, we too would start to suspect that maybe, just maybe, we were invincible. McG sure did, because once the fighting in Venezuela was over, he gathered up some troops and continued attacking surviving Spanish outposts.
In 1820, he landed in Nicaragua on the Mosquito Coast, named so for the Miskito people. (Although, yes, it incidentally had a bunch of mosquitos.) The Mosquito Coast was a generally unwelcoming piece of land. Swampy, flat, and warring tribal factions. It probably didn't take a lot for MacGregor to convince the local king, George Frederic Augustus I, to sign over the land to him to set up a colony. Although some sources say that Con Man wanted to be extra sure he got the rights to where Shrek would flee if he'd been a Nazi scientist, so he got George drunk before having him sign the land over. This is where MacGregor's legend truly begins.