Wagon Train to the Moon

We can't stop exploring the unknown. At least this time we're planning ahead. In centuries past the task of exploring and colonizing meant packing as much as you could carry and then, on faith alone, set out for places never seen with only a hope that anyone would survive. Abraham setting out from Haran; Columbus for the edge of the world; wagon trains into the west. How soon before there are people off-earth who've never set foot on this planet?