Source: SRI International (2002).
Mail delivery is illustrative of space / time convergence with significant improvements in the mid 19th and early 20th centuries. Delivering a parcel between New York and San Francisco in the early 1840s took about 180 days by carriage wagons. The use of a maritime road relying on an overland route through the Panama peninsula in 1847 reduced delivery times to 30 days and to 21 days once the Panama Canal railway was completed in 1859. In 1860, a combination of rail to St. Joseph, Missouri and the Pony Express to San Francisco reduced delivery times to 14 days. With the completion of transcontinental railway in 1869, 7 days were required. The first use of air mail in the 1920s improved the service to 4 days and jet planes reduced delivery times to less than 1 day in 1973 when overnight services were introduced.