Asphalt concrete (commonly known simply as “asphalt”), one of the world's most common materials for paving roads and streets, is made up of sand and stone bound by asphalt, a naturally occurring form of petroleum (oil or tar). It was first tried in the mid-1800s in Europe. It was also tried along New York City's Fifth Avenue, laid over the original paving of granite blocks, where it failed at first—black dust soiled the houses along the avenue. But after the manufacture of asphalt was improved, by the end of the century 1,500 miles of streets in more than 100 American cities were covered with asphalt, which drivers of wagons (horse-pulled vehicles) preferred to granite because its smoother surface offered less resistance to wagon wheels rolling over it, and the relatively soft pavement was gentler on horses' legs. Furthermore, whereas the grooves between granite paving stones had to be scraped clean by hand, sanitation workers could employ more mechanical means to sweep a smoothly paved asphalt street. This advantage gained for asphalt the strong support of public health advocates. Bicyclists, who were among the most vocal early advocates of a political movement to improve roads that originated in the late 1870s and flourished into the 1920s with the eventual support of early automobile enthusiasts, understandably also very much preferred asphalt over stone and gravel roads.

Sanitary and municipal engineers also favored asphalt, not only for its ability to allow for more efficient cleaning but also for its quieter traffic flow. Although local governments had the right to pave and maintain streets, property owners next to a road had traditionally been able to call for its paving and choose the kind of pavement they wished. Especially in crowded cities, the streets outside the downtown area served not only to carry traffic but also as gathering places and playgrounds when there were no nearby parks. As a result, the people living along a neighborhood street often wished to keep it unpaved or paved with gravel or cobblestones in order not to encourage traffic. However, the rapid rise of the automobile made it increasingly difficult to escape traffic completely. Fast-moving rubber-tired motor vehicles so tore up gravel pavements that they soon ceased to be a viable option in an urban area. Stone pavements were too rough for the speed at which autos traveled, and so asphalt—which was backed by a wide range of influential groups, from truck drivers to engineers—soon became the pavement of choice. This was especially the case when asphalt lakes and other naturally occurring sources of asphalt became readily available. These lakes, also known as tar pits, were formed where crude oil seeped to the surface, creating a large puddle of thick natural asphalt.

Oil had been discovered in Pennsylvania in 1859, but asphalt made from it contained a wax-like substance that froze in the winter and led to the cracking and deterioration of roads paved with it. The petroleum from California and Texas oil fields that opened up in the early twentieth century did not have so large a waxy component and so was more suitable to making good asphalt artificially. However, experience working with the still relatively new paving material had not kept up with the increasing diversity of its sources and composition. As was the case with many technologies of the time, standards were almost nonexistent and so results were uneven. A breakthrough came from the inventor Frederick J. Warren, who with his brothers founded a company that exploited a range of types and sizes of crushed stone in its asphalt mix.

By obtaining a government-protected patent in 1901, Warren was granted exclusive legal rights to manufacture and sell a new product he designed called Bitulithic. The angular stone chips—collectively known as aggregate—interlocked more effectively in the patented pavement and so provided a considerable improvement on contemporary paving systems. In fact, Warren's Bitulithic was so successful that competitors sought ways to get around the patent, which called for aggregate graded in size from one-half inch to three inches. These competitors used aggregate smaller than one-half inch in size, allowing pavements that were even more durable than pavements made with larger stone chips, which deteriorated rapidly with high automobile speeds.