A riverboat by the wharf at Mount Vernon circa 1936. Only steamboats that catered exclusively to white excursionists could use the wharf. (Library of Congress)

It is possible that no one is happier than Fairfax’s Dave Sullivan that steamboats once plied the Potomac River and the Chesapeake Bay, the subject of last week’s Answer Man column.

Dave’s parents, Ruth and Joseph, were among those drawn to Washington by government jobs after World War II: Ruth with the Agriculture Department, Joseph with the Army Map Service.

There was also another bit of business they were attending to, though unsuccessfully at first.

“A doctor told them that they were trying too hard,” Dave wrote. “He suggested that they needed to relax, just get away for a few days and see what happened.”

And so over the 1948 Fourth of July holiday, the couple traveled by boat from Washington to Norfolk.

“Well, the doctor’s advice was apparently just what my parents needed,” Dave wrote. Nine months and four days later, he was born at Doctors Hospital.

No steamboat, no Dave? Who can say?

Like all good Annapolitans, Bill Schneider has a sailboat. He’s also into traditional jazz and Dixieland music, with a house full of old phonograph records and wax cylinders. His favorite Edison cylinder is “Sailing Down the Chesapeake Bay,” a jaunty 1913 tune about the Old Dominion Line vessels that sailed between Baltimore and Virginia. “Come on, Nancy, put your best dress on,” goes the chorus. “Come on, Nancy, ’fore the steamboat’s gone.”

Bill pointed out that bands still perform the song these days, though they eliminate the racist language of the original. Rather than “darkies” humming a good ol’ tune, banjos are strumming a good ol’ tune.

That raises a question: Given that the steamboats in question plied Southern waters, how were African Americans treated?

Just about how you’d expect. Eastern Shore journalist and steamboat buff Jack Shaum said that the printed deck plans of some Chesapeake Bay steamers showed accommodations for “colored” passengers.

In addition to the steamboats that traveled longer distances in the bay — linking cities such as Baltimore, Washington and Norfolk — there were excursion steamboats that took passengers on day trips. These too were separated by race, both the vessels and the resorts to which they sailed.

“There was this whole parallel segregated amusement trade,” said Andrew Kahrl, a professor of history and African American studies at the University of Virginia and author of “The Land Was Ours: African American Beaches From Jim Crow to the Sunbelt South.”

Not at first, though. In the late 19th century, the segregation was not quite so absolute. While the races didn’t mix in the same places at the same times, some resorts had days designated for African American tourists. Marshall Hall, across the river from Mount Vernon, was one of those. Boats traveled there from the Seventh Street Wharf, sometimes carrying white passengers, sometimes black.

But attitudes hardened after the turn of the century. Marshall Hall became whites only. So did Mount Vernon. In 1904, the Ladies’ Association that ran George Washington’s plantation home decreed that only the Charles Macalester, a steamboat that catered exclusively to white excursionists, could use its wharf.

White steamboat owners were happy to make money from black tourists, offering black-only cruises to black-only beaches and picnicking grounds.

“African American businessmen tried to break into this industry by buying their own steamboats or renting out or leasing their own landing spots along the Potomac,” Andrew said.

The most successful was Lewis Jefferson, an entrepreneur who had substantial land holdings in Southwest Washington. In 1904, he purchased a side-wheeler, the Jane Moseley, and increased his stake in an amusement park in Prince George’s County called Notley Hall.

“This was a resort that was originally owned by a white family that would lease out its grounds periodically to African Americans,” Andrew said. “Eventually, it became almost exclusively for African American excursion parties.”

Jefferson made improvements and changed the name to Washington Park. It boasted a carousel, a penny arcade, a billiard hall, a restaurant, and a 5- and 10-cent theater. Another steamboat, the River Queen, also served the resort.

In a 2008 Journal of American History article, Andrew quotes an advertisement for Jefferson’s park: “If the colored men and women of this city are inclined to patronize nearby resorts, why not patronize one conducted by a member of their own race, rather than one conducted by a white man, a Jim Crow arrangement . . . with its separate wharf?”

Andrew said that Washington Park burned down around 1917. Today, nearly a century later, all sorts of tourists gather not far from where it once stood: National Harbor.

Twitter: @johnkelly

For previous columns, visit washingtonpost.com/johnkelly.