The year 1970 saw the debuts of two regional card & memorabilia shows that would become fairly prominent over the next decade: the Mid-Atlantic Sports Collectors Convention, and the Midwest Sports Collectors Convention, better known as the Detroit convention. The first Mid-Atlantic Convention took place in March or April 1970 (I'm not sure of the exact date) at the home of Crawford Foxwell, who wrote up a one-page account for issue #47 of The Ballcard Collector. That's the first article below.
On the page following Foxwell's article (see second page below) was an item about the inaugural Detroit collectors convention then being planned by Dennis Graye, Lloyd Toerpe, and Tom Altschuler. Two issues later, in Ballcard Collector #49, there was another item about the planned Detroit convention and the "flood of calls" coming in to the organizers. (See the third page below, right under the ad where Mike Aronstein was selling 19 T215s for $4 apiece (!!).) In Ballcard Collector #52 (mailed on September 3, 1970), Dick Reuss reported in his column (fourth page below) that the two-day convention was going to take place September 12 and 13 at the Detroit Hilton, where they had rented two whole rooms after Howard Johnson's had given the organizers "a big run-around". Finally, in the October 1970 issue of The Trader Speaks, co-organizer Lloyd Toerpe reported on the successful convention (last page below). They had 40 advance registrations, 15-20 who paid at the door, and 25 kids who dropped by. Woo hoo! It was so many people that they couldn't keep track! It's hard to believe that a show that size was such a big deal, but that was big for the time; most of the handful of conventions still took place in people's houses, like the Mid-Atlantic show described above, or the first three West Coast conventions, which took place in Jim Nowell's house. But within a few years, such shows, especially the Detroit show, would become much bigger than those first organizers probably dared imagine.
