 After further exploration , the Pilgrims chose a location in present @-@ day Plymouth Bay in late December 1620 as the site for their settlement . Standish provided important counsel on the placement of a small fort in which cannon were mounted , and on the layout of the first houses for maximum defensibility . Only one house ( consisting of a single room ) had been built when illness struck the settlers . Of the roughly 100 who first arrived , only 50 survived the first winter . Standish 's wife Rose died in January . 
