Okrent's 2010 masterpiece history was eventually titled Last Call: The Rise and Fall of Prohibition, and it serves as inspiration for the National Constitution Center's Prohibition exhibit, launching Friday through April.
I didn't exactly have to drag him over to McGillin's Olde Ale House for a few beers and conversation.
"I've wanted to come here for years," Okrent said, gazing at the memorabilia and 19th-century licenses on the walls of the city's oldest tavern. He lives in New York but visits Philly frequently, and he didn't have a problem finding the bar hidden on tiny Drury Street.
There's no evidence McGillin's was a speakeasy during Prohibition. But, being just a short stroll from the 300 block of Walnut, it still seemed an appropriate place to talk about how a city and a nation could at once renounce a simple pleasure while so willfully indulging in the same.
Okrent barely pulled a swallow from his glass of house IPA before launching into an answer.
"It's the difference between Quaker Philadelphia and immigrant Philadelphia," he said.
When Rush published his Moral and Physical Thermometer, which laid out the stages and consequences of drinking alcohol (from happiness to suicide) in 1784, the city was quite in the grips of the original English immigrants who followed William Penn.
"By the 1920s," Okrent said, "the population had totally changed."
Where much of the energy behind Prohibition came from conservative white Baptists and Methodists who held political power in the South and Midwest, by the time the 18th Amendment was enacted in 1919, the cities were teeming with African-Americans, and immigrants from Ireland, Germany and elsewhere.
So, Okrent noted, even as "Drys" like former Philadelphia Phillies outfielder and evangelist Billy Sunday could draw tens of thousands to anti-booze revivals, "Wets" placed orders for Kerper's notorious gin.
Two of the city's Prohibition-era characters in particular intrigue Okrent.
One is Max "Boo Boo" Hoff, a Jewish boxing promoter and head of Philadelphia's notorious Seventh Street Gang, who Okrent said "was bigger than [Al] Capone." Hoff made his money converting legal industrial alcohol into drinkable gin in a barely hidden operation that was protected by millions of dollars in payoffs to cops.
"Imagine the most corrupt police department in America," Okrent said.
"Philadelphia's was way beyond that . . . The ability to be a city cop was an invitation to bribery."
The other notable is Marine Gen. Smedley P. Butler, a Haverford School grad and two-time Medal of Honor winner known as "the Fighting Quaker."
He was granted leave from the Marines by President Coolidge and sent to Philadelphia in 1924 to clean up the city as director of public safety.
Guess who won that battle?
Butler was run out his job after less than two years, muttering, "Sherman was right about war, but he was never head of police in Philadelphia."
But it wasn't Hoff who beat Butler, Okrent said.
"The thing that did him in was he wanted to close down the Bellevue. That's where the mayor and the city's elite drank."
The 21st Amendment would end Prohibition in 1933, and America would try to forget that ugly chapter. But as we ordered another round of beers, Okrent seemed wistful about the distant era.
"It was much easier to get a drink during Prohibition than after Prohibition," he said.
"During Prohibition, you could get alcohol 24 hours a day, seven days a week. You could sell anything you want and pay no taxes.
"After Prohibition . . . " Okrent raised his pint toward the old liquor licenses hanging above our heads.
Today McGillin's, or any bar, can be shut down if it violates any of a thousand different rules. Hours of operation, taxes, underage drinking, health codes - the list is long.
"The truth is," Okrent said, "the arrival of appeal meant it was actually harder to get a drink."
"American Spirits: The Rise and Fall of Prohibition," Friday through April 28 at the National Constitution Center, 525 Arch St. The exhibit includes artifacts as varied as flapper dresses, the hatchet used by Carrie Nation to bust up saloons, and the first case of beer delivered to the White House upon repeal. Info and tickets: http://prohibition.constitution
"Joe Sixpack" is by Don Russell, director of Philly Beer Week. For more on the beer scene, sign up for his weekly email update at www.joesixpack.net. E-mail: firstname.lastname@example.org.