The drive from Columbia, Tennessee to Memphis, Tennessee is a straight shot west on Interstate 40 for approximately 116 miles (187 km), taking 1 hour 45 minutes to 2 hours.
From Columbia (Maury County seat), take US-412 West / SR-99 West to I-40 West at the I-40/US-412 interchange (Exit 146). Stay on I-40 West for ~100 miles through the rolling hills of the Western Highland Rim, across the Tennessee River at mile marker 126 (New Johnsonville area), through the Kentucky Lake/Tennessee River valley, past Jackson (major exit, services, Casey Jones Village), and into the Memphis metro at the Fayette/Shelby county line.
Columbia (pop. ~42,000) is the "Antebellum Homes Capital of Tennessee," home to James K. Polk's ancestral home and the Mule Day celebration (April). It's the gateway to Middle Tennessee's western edge—where the Central Basin meets the Highland Rim.