The 1958 Yankee Stadium/Polo Grounds assembly was notable but provided no great surge as I recall. We bragged about the attendance of 253,922 every chance we got. That attendance and the number of times the name Jehovah appears in the American Standard Version Bible, 6823, are indelibly scored in my brain.
A case can be made for 1966-1975 as the Golden Era of JWs:
1. The summer of 1966 saw the release of the book Life Everlasting in Freedom of the Sons of God detailing the chronology supporting the '75 speculation. That speculation sparked the rash of meeting parts, traveling overseer service talks that seriously implied that this "system" would end in 1975.
2. The release of the book The Truth That Leads to Eternal Life in 1968 and the subsequent 6 month study limitation.
3. Nightly news reports featuring casualties of the Vietnam War, U.S. cities burning do to civil unrest, the civil rights movement in the mid to late 60's, the violent '68 Democratic Convention in Chicago. JW's were clearly feeling the "Last Days."
4. Radical social change brought on by Haight Ashbury, The Beatles, Timothy Leary, the Weather Underground, Students for a Democratic Society, the Black Panthers, the Chicago 7, etc. Exciting times to be a JW!
5. Radical organizational changes mentioned at the 1971 district conventions: The elder arrangement implemented in 1972. Few seem to remember this, but there was even a talk at that assembly strongly hinting that field service time would no longer be counted. That was never implemented, of course.
tms