Chicago's relations with the wider world changed as its transportation links extended its geographical reach. The white areas on these four maps show how far a person could travel from Chicago by scheduled service in a 24-hour period, calculated for four dates at 50-year intervals since early in the city's history. In 1850, travel was restricted to lake and canal boat, stagecoach, and a single railroad line west of the city. Consequently, the zone of access with a day's travel reached little farther than Peoria, Milwaukee, and some other local centers within the region. By 1900, railroads had supplanted all other means of fast long-distance travel, and Chicagoans could reach most of the remainder of the United States and some parts of nearby Canada and Mexico within a day. In 1950, air service had joined railroads to extend 24-hour travel from Chicago (often in combination) to much of North and Central America, as well as some localities in Western Europe. By 2000, this combined reach, together with road service, had effectively expanded Chicago's reach to much of the rest of the well-populated world.