I have a toy train from the 1976 USA bicentennial. I was born in 1974, so it's the oldest thing I've owned since new.

Here's an example on YouTube: https://www.youtube.com/watch?v=4d4e_net1HQ

Made by Lionel to be a 'gotta catch them all' type deal, which they milked for four years if you wanted the full 15 piece set (engine, caboose, and 13 boxcars for the 13 original colonies). I do not have them all, but both my dad & I each had the engine, and between us we had enough of the common cars to build a nice enough playset to run around the Christmas tree.

Mildly interesting, in that Lionel can build some really nice toys, but this was not one of them. Train collectors call this generation the "Mostly Plastic Crap" era, and this set solidly ticks that box. Perhaps interesting (or frustrating), Lionel also made quality stuff during this exact same timeframe. You just had to know what to look for. But in hindsight, probably a good thing this was cheap. If it had been a nice set, I wouldn't have gotten to play with it as a 2 year old...

Over the years I've updated these engines with the better parts, I'd argue they run better than when they were new. Quite proud of that - as a kid I ran my engine until it simply could not run any more. Decades later I was able to not only repair it, but improve it. It will not ever be valuable, but it still makes me happy when I pull them out & run them around. Really triggers the old memories.