Selected in the third round (86th overall) of the 1976 NFL Draft out of Jackson State—where he played alongside Walter Payton—Jackie Slater arrived in Los Angeles as a backup before becoming the standard for offensive-line longevity. Spending his first three seasons primarily on special teams and as a reserve, Slater absorbed the professional game until taking over as the full-time starting right tackle in 1979. That year, he helped anchor an offensive line that led the Rams to an NFC Championship and a berth in Super Bowl XIV against the Pittsburgh Steelers.

Once entrenched at right tackle, Slater launched a reign of relentless durability that defined two decades in Southern California. From 1979 onward, he was a steady fixture on the edge, starting 211 regular-season games for the franchise. Opposing edge rushers struggled to solve his technique, as his combination of lateral footwork and brute strength neutralized the league's most fearsome pass rushers throughout the 1980s.

Slater earned seven Pro Bowl selections (1983, 1985, 1986, 1987, 1988, 1989, and 1990) and four Second-Team AP All-Pro honors. Whether blocking for Eric Dickerson during his record-breaking 2,105-yard rushing campaign in 1984 or protecting signal-callers like Vince Ferragamo and Jim Everett, Slater consistently anchored one of the league's most dominant front fives.

His 20-season career with a single franchise set an NFL record for offensive linemen, spanning 19 years in Los Angeles (1976–1994) and concluding with a single final game after the team relocated to St. Louis in 1995. By the time he retired, Slater had blocked for 24 different quarterbacks and 37 different running backs, leaving behind an unmatched standard of consistency and professional dedication.

In 1996, the franchise permanently honored his legendary service by retiring his #78 jersey. His transcendent career achieved ultimate gridiron immortality in 2001, when he was enshrined in the Pro Football Hall of Fame in Canton, Ohio.