The Dow Jones Industrial Average breached the 23,000-mark for the first time on Tuesday, driven by strong earnings from UnitedHealth and Johnson & Johnson, but the S&P 500 was flat.
The blue-chip index has surpassed four similar 1,000-point milestones this year, indicating investor faith in the bull-run despite lofty stock valuations.
But the Dow was unable to hold the level and has been trading below 23,000 for much of the afternoon.