Nat Hiken's Car 54, Where Are You focused on 2 beat patrolmen, though it was really an ensemble comedy. It lasted two seasons.
Don Adams' first post-Get Smart series, The Partners, lasted 1 year. That was largely because of the fact that NBC put it on Fridays, opposite The Brady Bunch. Enough said.
It wasn't until a veteran comedy writer, Danny Arnold, came up with a winning formula in the 1974-5 season that there was a police sitcom that actually worked.
Barney Miller debuted in January 1975, after a pilot had aired the preceding summer. Arnold & Theodore Flicker created the staff of the 12th Precinct as a diverse group of personalities, a virtual melting pot, representing various ethnic groups. Miller (Hal Linden) was of Irish background, and the first season put equal emphasis on his personal & professional lives. However, wife Elizabeth (Barbara Barrie) was gradually phased out of the series after season 2.
Meanwhile, the staff evolved into a unit that we could all wish represented our communities:
Chano (Gregory Sierra, Sanford & Son) was a Latino detective whose quick temper led to fits of rapid-fire Spanish. Sierra left the series after 2 seasons, and returned to Sanford to reprise his role there as Julio during that series' final season.
Wojo (Max Gail) was a stereotypical Polish-American--naive, none-too-bright, and early on was also quick tempered.
Yemana (Jack Soo, ex-Valentine's Day) seemed to be more interested in looking for a sure thing at the track. Soo passed away in 1979, during season 5.
Harris (Ron Glass) eventually became an author during the course of the series' run. Glass & Soo were added to the opening credits in season 2.
Fish (Abe Vigoda) was the elder statesman, a veteran cop who was a couple of years away from retiring, but also seemingly was hen-pecked. Wife Bernice (Florence Stanley) made her debut in season 1, and would appear infrequently during the first three seasons, although another actress filled in for one episode. The Fishes left after the third season, spun off into their own series, Fish.
To fill the void created by Fish's retirement, Arthur Dietrich (Steve Landesberg) joined the squad, added to the opening credits in season 4. A virtual walking encyclopedia of knowledge, Dietrich befuddled co-workers and suspects alike.
During season 1, there were a couple of short-term officers. Wilson (Rod Perry) went undercover in drag in his only appearance. Perry moved on to S.W.A.T. the following season and Wilson was never heard from again. Janice Wentworth (Linda Lavin) appeared in 2 episodes in the first season, even though she'd already been promoted to the vice squad after her first appearance. Of course, Lavin left to star in Alice.
The season 1 DVD features guest appearances by a number of familiar faces, including Vic Tayback (pre-Alice), Brett Somers (Match Game), Marla Gibbs (The Jeffersons), Howard Platt (Sanford & Son), & Nancy Dussault (later of Too Close For Comfort).
Following is a montage of opens from the first four seasons. Ron Carey (Levitt) was added around season 4 as well, became more of a regular after Jack Soo passed away.
While still working on Miller, Hal Linden added the Sunday morning children's show, Animals, Animals, Animals, and the daily interstital segment, FYI, to his workload. He'd only get one more primetime series, the short-lived Blacke's Magic, near the end of the 80's.