To be quite honest, I'm not really sure about my first Amtrak ride. I know I rode the Silverliner service to Harrisburg in June 1971, but I believe that the service was still being run by the Penn Central at the time. I may have made a joyride on a NEC train, though after May 1, 1970, I was getting pretty busy dealing with my high school graduation. In any event, the experience on the Amtrak NEC trains in the early 1970s weren't really much different from the experience on the Penn Central NEC trains.
That summer I worked at a camp, and thus had no time or opportunity for joy-riding. At the end of the camp session in August, I got bussed back to New York and had to make my way home from there. I remember riding on the Southern Crescent, which was hauled by Amtrak to Washington, and which had a few Amtrak cars clipped on for the corridor riders. I got stuck in an old ex-PRR P-70 which had been repainted in Penn Central green, but had no air conditioning. Rolling down the NEC at 100 mph with the windows open in this old antique was quite the experience!
After that, I spent a gap year in Israel and had no opportunity to ride Amtrak. I rode the Silverliner Service to Harrisburg when I returned in August 1972, but that was still being run by Penn Central. (Amtrak didn't take over operation until October 1972.) The train was terminated at Lancaster due to flood damage from Tropical Storm Agnes, and we were bustituted into Harrisburg.
Then I went off to a college in Wisconsin that was 90 miles from the nearest Amtrak station. I definitely know I rode an Amtrak train in April 1973, when I returned home for Spring break riding the Broadway Limited, and returned back to school the same way.