Crude oil began to be refined on a recognizable, industrial scale in the mid‑19th century, with key milestones between about 1849 and 1857. Earlier, people used small amounts of naturally seeping petroleum, but not in true refineries.

Earliest refining experiments

Historians usually point to experiments in the 1840s–1850s as the first intentional refining of crude oil into distinct products.

  • In 1849, Scottish chemist James Young distilled illuminating oil (kerosene) from seep oil and patented his process in 1850.
  • These early stills used simple distillation: heating crude and condensing vapors into separate fractions like kerosene and naphtha.

First commercial refineries

By the 1850s, crude oil refining shifted from experiments to commercial operations.

  • Samuel Kier in Pittsburgh built what is widely cited as the first U.S. commercial petroleum refinery around 1850 to distill kerosene from “rock oil.”
  • The first large, purpose‑built modern refinery opened in Ploiești, Romania, in 1856–1857, processing crude on an industrial scale.

Link to early oil wells

The growth of refining closely followed the first successful oil wells.

  • Commercial drilling in Ontario (1858) and Titusville, Pennsylvania (1859) suddenly supplied enough crude to make refining a major industry.
  • As output rose, refineries expanded beyond lamp kerosene to produce other fractions, though gasoline remained a minor by‑product until engines spread.

Information gathered from public forums or data available on the internet and portrayed here.