New York ? On May 23, 1903, one hundred years after Meriwether Lewis got his marching orders from President Thomas Jefferson, another historic American journey began — the first coast-to-coast automobile trip.

Now, another hundred years later, master filmmaker Ken Burns and writer David Duncan have brought the little-known adventure of Horatio Nelson Jackson to life. “Horatio’s Drive: America’s First Road Trip” airs at 8 p.m. Monday on PBS.

“This is a country that loves firsts, that loves its cars, and that loves road trips,” said Burns from Florentine Films, his Manhattan headquarters. “Why we aren’t taught about the first automobile road trip, I just can’t figure out.”

Burns learned of the story in 1990 from Duncan, who spent nearly a decade locating photographs, scrapbooks and finally Jackson’s granddaughters, who still had his many letters home. Those letters reflect Jackson’s humor, his affection for his wife, Bertha, and, most important, his unflagging optimism in the face of seemingly insurmountable car troubles and navigational snafus.

“The worst of it is over” and “just watch me now” were Jackson’s constant refrains.

Unlike the meticulously planned Lewis and Clark expedition, Jackson took off from San Francisco on a whim after betting $50 at a gentleman’s club that he could drive to New York in under 90 days.

Four days later, after purchasing a 1903 Winton touring car for $3,000 and hiring a driving companion, mechanic Sewall Crocker, he set off to do what several accomplished motorists before him couldn’t. Despite the fact that there were only 150 miles of paved road in the entire country, he and Crocker — and a goggle-wearing bulldog named Bud — arrived in New York on July 26, exactly 63 days, 12 hours and 30 minutes after leaving San Francisco.

Along the way, they got lost numerous times, endured almost every mechanical failure possible and created a media sensation as papers across the country tracked their progress against two rival teams that set out after them.

But Jackson’s never-before-published letters to Bertha — whom he inexplicably called Swipes — are the real star of the film.

On June 21, after a night spent lost in western Wyoming with no food, Jackson described it as the night that “thirty thousand mosquitoes died on the back of my neck,” adding that both he and Crocker “were stealing speculative glances at Bud as we tightened our belts.”

Horatio Nelson Jackson, left, mechanic Sewall Crocker and a bulldog named Bud drive through Vermont. Jackson's historic American journey, the first coast-to-coast automobile trip, is brought to the small screen in Horatios Drive: Americas