I'd like to add a little context to the excellent information above.
In the early 60's, WPGC and WEAM both got excellent ratings. WPGC was 10KW but highly directional from southeast of the District. WEAM had 5KW from just over the Falls Church line but did not have the best signal. At night WEAM had a lot of background in the northeast segment of the market. WINX ("Winks"), with 1KW day and 500 watts at night, had a following in Montgomery County north of the District.
The reason WPGC and WEAM did so well is because Washington did not have a Top-40 station with a good signal. In fact, the market had little in the way of big signals. The best signals were WMAL, WRC, WTOP and WWDC.
WWDC: Yes, Carroll James is said to have played the first Beatles record. But I didn't consider WWDC to be a Top-40 station; they played Top 40 music but within an adult, full-service framework.
Because the market had so many poor signals, FM took off early here. WPGC-FM simulcasted its daytime AM. In 1966, WPGC hired popular DC personality Jack Alix for evenings and started going all out to get people over to the FM dial. At AM sign-off, they would tell listeners to move to 95.5. Around 1971, WPGC-FM increased from 15,700 to 50,000 watts and became a ratings juggernaut, eventually burying WEAM. By the mid-70's, WPGC was challenging WMAL-AM for #1 and beat WMAL in some books.
DC Top-40 radio sounded really good in the 60's and 70's despite 3 reputedly crazy GM's. Someone mentioned Harry Averill. Every WEAM jock had one thing in common: Harry would eventually fire them. He embraced the jock du jour plan. I've heard from a former WEAM employee that Harry had mics buried in the ceiling in order to hear what employees were saying. I also heard Harry kept secret where he would be buried because he knew what former employees would do.
WPGC's GM, Bob Howard (aka Mr. Soundoff) was said to monitor jocks, and call up and scream at them. He decided to use house names. He fired Bob Raleigh when Raleigh asked for a raise, and Raleigh went over to WWDC. Bob Howard then kept the Bob Raleigh name at WPGC, and there were several Bob Raleigh's after that. He named Dean Griffith, who later went to WMCA as Dean Anthony, after Griffith Stadium, where the Washington Senators played. And of course when Dino left, Howard brought in the next Dean Griffith. Richard Eaton, GM at WINX, was mercurial and cheap according to his reputation.