Fifty-five years ago, Oliver Koppell came to Harvard as a young man with a big idea: to create a travel guide for those who thought travel was beyond their reach.

The 18-year-old entrepreneur found the perfect partner to launch his plan into action: Harvard Student Agencies (HSA). On the floor of his freshman dorm room, Koppell crafted 25 pages of advertisements, brochures, and tips on touring Europe. With the 1960 European Guide in hand, three planeloads of HSA customers set off for Europe, and the travel-guide world would never be the same. Since then, HSA and Let’s Go have constantly succeeded in realizing the dream of accessible budget travel. The enterprising Koppell convinced HSA to take the helpful tips from the 1960 European Guide and turn it into an annual title called Let’s Go: The Student Guide to Europe.

Koppell assembled a staff of fellow students, and the Let’s Go team was born. From the very first edition, Let’s Go combined budget tips with trademark wit and irreverence. For example, Let’s Go guaranteed early readers a trip from Europe to Asia that would cost only four cents: the ferry ride across the Bosphorus in Istanbul, Turkey. Young travelers certainly appreciated that there was a travel guide written for them, for a change, and it showed. From 64 pages and 6500 copies of the 1961 edition, Let’s Go: Europe shot up to 321 pages and 65,000 copies in 1968.

The Let’s Go universe kept on expanding when its business manager, Andrew Tobias, was interviewed on the Today Show in 1966. Sales skyrocketed almost immediately, and glowing reviews flooded in from Newsweek, Time, The New York Times, and others. Before long, the students at Let’s Go had become the pilots of a professional company, and in 1971 Let’s Go partnered with its first professional publisher, EP Dutton.

Let’s Go’s success had led the team to introduce Let’s Go II: The Student Guide to Adventure in 1968. The next year, they released an early version of Let’s Go: USA. After years of continued effort, Let’s Go introduced a permanent line of regional guides, starting with Let’s Go: Britain & Ireland in 1976. After sky-high sales left Dutton drooling for more, they followed with Let’s Go: France in 1978 and Let’s Go: Italy in 1979. In 1982, Let’s Go enlisted St. Martin’s Press as its new publisher, reflecting the increasing size of the budget-travel market.

Meanwhile, the team kept adding destinations at full throttle. The title line expanded from six titles in 1981 to 10 after 1985. That year, the first edition of Let’s Go: Mexico sold more copies than any previous debut guide. By 1986, almost 500,000 Let’s Go books were being produced, hitting the shelves just three months after being researched—light-years ahead of the competition. The young trail-blazers at Let’s Go continued to embrace modernity when the 1986 team computerized the entire series. In 1988, as another new title was launched, Let’s Go’s total readership was up to 1,600,000.

Always strong believers that good things come in small packages, Let’s Go introduced its innovative city guides in 1991. Although new in name and layout, titles like Let’s Go: London and Let’s Go: New York City kept dishing out the same budget wisdom that had driven a generation of Let’s Goers.

Even as readership soared to 3,500,000 in 1993, Let’s Go never let success go to its collective head. It gave back to the budget community by sending researchers to even more varied destinations. En route to 24 guides in 1997, Let’s Go expanded to South America for the first time. The very next year, pioneering researchers planted the Let’s Go flag in a sixth continent with the release of Australia and New Zealand guides.

With the dawn of the internet, a large market emerged with much of the same budget sensibilities as Let’s Go. As early as 1996, www.letsgo.com was up and running, its launch sponsored by American Express. Let’s Go also carried its penchant for new media into the world of television, giving tours to viewers of CNN’s “Travel Guide.” Before long, city guides had even gone digital, available for download on PDAs.

Still anchored to its student mission, in 2001 the Let’s Go team organized a two-month roadtrip to universities across the East Coast. Its book giveaways and free travel advice were astronomically successful with the college crowd. That summer, nearly 200 researchers worked on the 2002 series, which had grown to include new titles like Let’s Go: China. The roadtrip idea stuck with Let’s Go through 2007, when the outreach continued with a repeat voyage through the Midwest.

For 2003, an excited staff engineered an ambitious series relaunch, both inside the covers and out. They introduced Price Diversity, a scale for the “budget factor” of accommodations and restaurants, along with pithy sidebar features. Most important, however, was the inclusion of ways for travelers to give back to destinations through volunteer work or study abroad. Proving that you can’t keep a healthy social conscience down, Beyond Tourism has become the most rewarding chapter in any Let’s Go book.

And, of course, the team picked up right where it had left off in bringing more books to the shelves. In 2003, 2004, and 2005, Let’s Go added a total of 11 new titles, boosting the total to 48. 2009’s Let’s Go: Buenos Aires brought the count to 49. The 2011 series saw Let’s Go’s focus return to Europe, its bread and delicious butter; nearly all of the coverage was rewritten from scratch to ensure the highest quality prose and information.

In 2012 Let’s Go introduced a line of Budget Guides, 11 titles devoted to individual cities and meant to maximize budget travelers’ experience. 2012 also saw the development and launch of the Explore walking-tour apps and the Let’s Go app for iOS and Android, as well as the advent of the new www.letsgo.com.

In 2013, Let’s Go increased their app line to include Nooks as well as push out a consolidated iOS app through which users could purchase full guides without leaving the app experience. There was also the introduction of Campus Teams through which recruits from Ivy League and colleges around the Boston area set up their own local Let’s Go groups through which they could blog and extend their audience to students browsing the Let’s Go website.