Commissioned by the French government in 1673, Louis Joliet and Father Jacques Marquette became the first explorers of Chicago. Around 1780, Chicago’s first permanent settler, Jean Baptiste Point DuSable, and his family came to the area. The town of Chicago expanded its boundaries and became a city in March of 1837. The development of the railroad and the Illinois/Michigan Canal in 1848 proved necessary for Chicago’s growth. Both helped the city become prominent in the cattle, hog, lumber, and wheat industries and the city’s population tripled in the six years following the opening of the canal. As the city continued to grow, there were setbacks along the way, one of the largest being the Great Chicago Fire of 1871, which became a turning point in the history of the city. The citizens of Chicago resurrected the city and even built momentum for more development after the fire. By 1900, Chicago had built the longest cable car and streetcar lines in the world and managed to reverse the flow of the Chicago River. Also during this time, the city became second only to New York in manufacturing activities, and first in the meat packing and rail industries. The remainder of the 20th century brought more architectural advances to Chicago. The Sears Tower (now known as the Willis Tower) was completed in 1973, making Chicago home to the then-tallest building in the world.