The United States Census Bureau says that the city has a total area of 15.9 kmÂ ( 6.1 miÂ ) . 15.3 kmÂ ( 5.9 miÂ ) of it is land and 0.6 kmÂ ( 0.2 miÂ ) of it is water . According to the United States Census Bureau , the city has a total area of 6.1 square miles ( 15.9 kmÂ ) , of which , 5.9 square miles ( 15.3 kmÂ ) of it is land and 0.2 square miles ( 0.6 kmÂ ) or 3.75 percent of it is water .