<a href="https://en.wikipedia.org/wiki/Petroleum" id="mwjw" rel="mw:WikiLink" title="Petroleum">Petroleum</a> is discovered in <a href="https://en.wikipedia.org/wiki/Titusville,_Pennsylvania" id="mwkA" rel="mw:WikiLink" title="Titusville, Pennsylvania">Titusville, Pennsylvania</a>, leading to the world's first commercially successful <a href="https://en.wikipedia.org/wiki/Oil_well" id="mwkQ" rel="mw:WikiLink" title="Oil well">oil well</a>.