The 1807 act of the New York State Legislature instructed the commissioners to erect “suitable and durable monuments at the most conspicuous angles.” These locations, which are noted on the 1811 plan, guided the future layout of streets. Randel continued erecting monuments during his survey work from 1811 to 1818. By his count, he erected 1,549 monuments and 98 iron bolts, where ground rock required the substitution.