The Russell 2000 index surged over 4% higher after Donald Trump was confirmed as the winner of the US presidential election.
In the first half-hour of trading on Wednesday, the index of small and mid-cap stocks rose 94 points or 4.15% to 2,354.7.
As a domestically-focused index, the Russell 2000 outperformed the more international indexes such as the S&P 500, Nasdaq Composite and Dow Jones, which rose 1.7%, 1.9% and 3% respectively.
US markets generally outperformed others overseas, which analysts at UBS said was likely on the anticipation of stronger domestic growth, increased M&A activity, an extension to personal tax cuts, and hopes of lower corporate taxes.
Economic elements of Trump's campaign included extending personal income tax cuts, lowering corporate taxes, deregulation, trade tariffs and controlling immigration.
The strong jump for the Russell 2000 is "a positive reaction to the Trump win, as he is seen as considerably more friendly to small US companies than Harris, due to his promise to cut taxes and tear up regulations", said market analyst David Morrison at Trade Nation.
"But Trump has also promised to increase tariffs in both scope and size. Again, this is probably more of a boost for domestically-focused corporations, although many economists argue that it will become a headwind for the US economy overall."
Big risers on the Russell index included GEO Group Inc rising 33%, Cytek Biosciences Inc up 31%, CoreCivic Inc and MasterCraft Boat Holdings Inc climbing 25%, Treace Medical Concepts Inc and Rayonier Advanced Materials Inc gaining 23%.
Fallers included renewable energy like Sunnova Energy International Inc (down 42%), Array Technologies Inc (down 20%), wind turbine maker TPI Composites Inc (down 21%) and Shoals Technologies Group Inc and Altus Power Inc (both down 16%).
Roomba robot vacuum cleaner maker iRobot Corp, along with PACS Group and Tango Therapeutics, all fell sharply following earnings releases.