1. Starting Point: Portland, Oregon
2. Head East on I-84: Take I-84 east from Portland, passing through the Columbia River Gorge and into Idaho.
3. Continue on I-80: Merge onto I-80 in Ontario, Oregon, and continue eastward through Idaho, Wyoming, and Nebraska.
4. Take I-76 East: Near Big Springs, Nebraska, take I-76 east towards Denver, Colorado.
5. Proceed South on I-25: In Denver, merge onto I-25 south and continue through Colorado and New Mexico.
6. Take I-40 East: Near Santa Rosa, New Mexico, take I-40 east towards Amarillo, Texas.
7. Continue South on I-40: Pass through Amarillo and continue south through the Texas Panhandle.
8. Reach Harlingen, Texas: I-40 will take you directly into Harlingen, Texas.
Remember that this route may vary depending on your departure point in Portland and any specific stops or detours you choose to make along the way. It's always a good idea to check the latest traffic updates, road conditions, and weather forecasts before embarking on a long road trip.