 Lafayette is a six by six mile square, except that the north side is irregular, following the course of the Yellow River.According to the United States Census Bureau, the town has a total area of 39.1 square miles (101.3 km²), of which 34.5 square miles (89.4 km²) is land and 4.6 square miles (11.9 km²) (11.74%) is water.The six by six mile squares that became Lafayette were first surveyed in the fall of 1848 by crews working for the U.S. government.