Not enough information about the trust to answer.

I would say there's a 95% chance that this was a typical revocable living trust with assets that got stepped-up basis when the second spouse died.  But I'll give it a 5% chance that it was an irrevocable trust, perhaps set up by the grandparents in 1949, to pick a year at random.  I have clients who are selling assets from an irrevocable trust, established in 2006, when the husband died.  The income went to the wife, but the principal now goes to his two kids from a prior marriage.  It doesn't include any Amazon stock, but if it did we would have a large capital gain.