The Dow Jones Industrial Average (DJIA) has broken through the 20,000-point mark for the first time ever, crossing a symbolic line only a year after falling below 16,000.
The index has surged over 2016, with the election of Donald Trump prompting a massive increase in US share prices in the last two months of 2017.
The index, which tracks the prices of shares in 30 of the most familiar blue chip stocks on Wall Street, opened at 19,999.48 points, before edging up. Its constituents include Coca-Cola, Apple, Disney, and IBM, amongst many other household names.
The US President's official Twitter account (as opposed to his personal account) greeted the news with a single word: "Great".
Two other benchmark indices, the S&P 500 and the Nasdaq Composite, also reached record highs on Wednesday.
Professional investors take little note of movements in the Dow Jones, as it measures only share prices without weighting stocks by market capitalisation (as the S&P 500, FTSE 100 and most other major indices do).
Nevertheless, it is a hugely symbolic measure of the fortunes of corporate America, with a history stretching back to 26 May 1896, when it was unveiled by Charles Dow, one of the founders of the Wall Street Journal.
The end of 2016 will form a notable part of that long history, with the election of Trump as US President prompting a string of record-breaking highs.
Trump's campaign promises of a massive increase in infrastructure spending coupled with big tax breaks and deregulation prompted a huge movement of investor money from bonds into stocks in anticipation of higher growth.
However, in recent weeks that growth has been tempered as investors wait for more detail on the economic policies of Trump. The DJIA has tracked that sentiment, with the pace of gains slowing and struggling to break the symbolic (if largely meaningless) 20,000 value.
Trump has since started to implement some actual policies, with executive orders allowing controversial oil pipelines and freezing new regulations.
Trump also reiterated his promise to build a border wall with Mexico on Twitter, boosting industrial stocks such as Caterpillar, a DJIA constituent.
The US economy has shown signs of strong performance over the past few months. Third-quarter annualised GDP growth hit 3.5 per cent in 2016, with the performance for the last three months of the year to be reported on Friday.
Kully Samra, UK managing director at Charles Schwab, said: “The Dow moving up and over 20,000 is a sign of an exceptionally strong US economy. There is no question that we are witnessing a surge in business, consumer and investor confidence, in keeping with the more business-friendly policies of the Trump administration.
"The market’s performance today is more than a 'Trump Bump'; it is yet another indication that we are in an ongoing secular bull market in US stocks, with low near-term recession risk and that this should continue for some time, irrespective of the political administration,” he added.