When the Dallas Cowboys selected University of Iowa consensus All-American John Niland fifth overall in the 1966 NFL Draft, they made franchise history before he ever put on a helmet. Niland became the first offensive lineman Dallas selected in the first round, establishing a blueprint for heavy-investment blocking units that would define the organization across multiple generations.

Niland spent his rookie year being baptized in fire, starting four games and squaring off daily in practice against legendary defensive tackle Bob Lilly. Iron sharpened iron; refining his technique against Lilly transformed Niland into a dominant interior force. By 1967, he had taken full ownership of the starting left guard spot, using his low-pad balance and athletic, pulling-guard agility to spearhead Tom Landry's "Multiple Offense."

Between 1968 and 1973, Niland put together a stretch of interior line play matched by few guards of his era. He earned six consecutive Pro Bowl nods and three First-Team All-Pro honors (1969, 1971, and 1972). Niland was the relentless motor on an offensive line that annually led the league in total offense and rushing yards, paving lanes for Duane Thomas, Walt Garrison, and Calvin Hill.

His finest hour arrived during the 1971 postseason, culminating in Super Bowl VI. Niland and the Dallas front wall completely neutralized the Miami Dolphins' front seven, paving the way for a then-record 252 rushing yards in a 24–3 victory that delivered the franchise's first Lombardi Trophy.

Niland's nine-year tenure in Dallas was marked by remarkable durability, missing just two games across 124 regular-season contests. After a final full season in Big D in 1974, he was traded to the division-rival Philadelphia Eagles, playing one final season before retiring after the 1975 campaign.

With Dallas, Niland played 124 regular-season games (111 starts), 15 postseason contests, and two Super Bowls. A six-time Pro Bowler, three-time First-Team All-Pro, Super Bowl VI champion, and Cowboys' All-Time Team member, he is one of six offensive linemen in franchise history with at least six Pro Bowls.