"Both musical traditions continue, still following the original styles of singing. In February 1963, about 1000 singers met at the National Guard Armory in Marshall for the Ark-La-Tex-Oma, four-state singing convention, while a meager forty-six souls continue to sing the Sacred Harp songs at Lone Pilgrim Church in Upshur County."
I found this quote in "The Fa-Sol-La or the Do-Re-Mi" by Louis Daigle. This is an article published in The Texas Historian, Volume 37, Number 5, May 1977, p. 7 by the Texas State Historical Association. It isn't an apples to apples comparison, since the author is comparing a four-state 7-shape note gospel singing convention to a local Sacred Harp singing. But here's another thing I find interesting. Some 50 years after the year referenced, it appears that the Ark-La-Tex-Oma Singing Convention was no longer in existence. In contrast, the Sacred Harp was still plodding along -- 363 people attended the East Texas Sacred Harp Convention, including people from 9 states and 2 foreign countries. (Not quite 1000, but a lot better than zero.)