It seems like no matter where you turn, Idaho offers something new, beautiful, and historic to explore. For your next road trip, take a scenic journey through Northern Idaho, meandering with ease across a fantastic landscape that was once thought to be impenetrable by all except one man: John Mullan. He was tasked with devising a way to connect the vital outpost at Fort Benton in Montana, the head of navigation on the Missouri, with Walla Walla near the highly navigable waters of the Columbia. While the Columbia was already accessible further south via the Oregon Trail, this new trail blazed across the forested mountain landscape of the Idaho Panhandle with greater ease than the terrain of the arid Southern Idaho desert.

Today, Interstate 90 follows the original Mullan Road closely, but not exactly. In fact, one of Idaho's greatest unsolved mysteries is discovering precisely where John Mullan's original road went. This adventure will take you from border to border, and will offer nearly unlimited opportunities for urban exploration, recreation, beach lounging, and much more... and even offer some off-road opportunities for you and the family to hunt for old wagon ruts. Check it out!

Here, in the rugged forests of Northern Idaho, looking down towards Mullan, one can see why Lewis and Clark struggled to navigate this challenging and diverse landscape over 200 years ago.

The Corps of Discovery were heroically searching for a means of reaching the Pacific Ocean. At the time, it simply didn't seem feasible.

But John Mullan never imagined that this historic road -- the first to cross the Rockies -- would eventually pave the way for Idaho's economic development, or the blossoming of the Northwest as a region.

The Mullan Road was built between 1859-60, which was when Idaho's logging and mining industries were in their prime. Without this pass from Montana to Washington, miners and workers would have struggled to enter the state from the north -- and Idaho's historic past would never have come to pass.

Starting in Post Falls, you can travel I-90 all the way to the Montana border (and beyond).

Along the way, you'll have the opportunity to explore the Mission of the Sacred Heart Historical Park in Cataldo, as well as be within easy access to the Trail of the Coeur d'Alenes, Route of the Hiawatha, dozens of sandy beaches, and hundreds of hiking trails for every activity level.

The Mullan Road Historical Site just off of I-90 memorializes John Mullan's name with a "Mullan Statute." Numerous others can be found at key points of the route all across Washington and Montana as well.

At one time, a white pine showcased the carved initials of Mullan and his men, but has since been removed.

This stretch of the original Mullan Road is preserved as a nature trail, leading to where the Mullan Tree once stood.

The original Mullan Road was used for only a brief decade before the transcontinental railroad rendered the pass obsolete. This can be found near Fourth of July Pass.

Keep your eyes open, and you might just see the remnants of wagon ruts.

Just outside of Mullan, you can find the lovely cascades of Elmer's Fountain.

Built by hand by a former miner from reclaimed mining scraps, the fountains access the natural spring running underground and create a picturesque scene and tribute to Henry James' best friend and mentor, Arthur Daily.

Mullan itself is a charming town that preserves the best parts of Idaho history.

Here, you can explore the fascinating Mullan Museum, stay at the highly-rated Mullan House, or simply find a nearby hiking trail.

While Mullan is little remembered for his feat of engineering with the development of the Mullan Road, his name is preserved throughout the area in the city of Mullan, the Mullan Pass, the Mullan Tree and historical site, and much more.

Lookout Pass makes a picturesque end to the Idaho portion of the Mullan Road.

What a historic journey!

While Lewis and Clark have undoubtedly received most of the glory for their discovery and shaping of the west, Mullan -- a first lieutenant in the US Army -- accomplished the very engineering landmark in the 1850s that exceeded everything the two pioneer explorers could have imagined.

What an adventure! For more Idaho road trips or summer adventure ideas, check out this One Easy but Unforgettable Hike, this Beautiful Back-Country Road Trip, or our list of 11 Amazing Scenic Overlooks across the state.