The road connecting Ploiesti to Brasov opened in 1864, and the railway arrived in 1882. Many schools and hospitals were built around this time. By 1939, the 12 refineries in Ploiesti provided 80 percent of the total petroleum processed in Romania. During the Second World War, these refineries suffered intense bombardment, the heaviest in the country, and most of the nearby residential areas, industrial compounds, roads and railways were destroyed.

The city has been revitalised to become one of the most important economic centres in Romania. The municipal economy is now characterised by a concentration of large businesses. There are plans to make Ploiesti the nucleus of a metropolitan area that will encompass eight nearby villages, which will add around 70,000 new inhabitants to the administrative area.

In 2002, the Ploiesti Municipality Strategy for Sustainable Development was produced with the support of the United Nations Development Programme.

Under CIVITAS II, the first pedestrian zones and bike lanes were built, supporting a new car-free zone that included controlled parking nearby and priority for public transport vehicles. The new car-free zone in Ploiesti and the supporting actions to encourage clean transport resulted in traffic in the immediate areas falling by 11 percent and localised air pollution dropping by 10 to 13 percent. In addition, new freight routes were signposted to take trucks around the city centre, although there was a lack of meaningful cooperation among freight companies and the high start-up costs may have contributed to the disappointing results in this area.