The Dow Jones Industrial Average goes back to May 26, 1896. Richard Sylla goes a lot farther back than that.

Sylla, an economist at the Stern School of Business at New York University and chairman of the Museum of American Finance, is one of the nation’s most eminent financial historians. He is a natural source to put the Dow’s latest record in long-term context.

The historical perspective, Sylla tells me in this recent video interview, suggests that “if we’re lucky we may see a series of these all-time highs.” He adds wryly, “There are such things as bull markets.”...