<prompt> Human: So, I recently did my taxes for the first time separate from my parents a couple years ago. At that time, I discovered an account my grandparents had opened for me years ago, with basically an all-star lineup of late 90s companies Dell, eBay, HP, etc. Im now looking to sell some of them to modernize the portfolio a little, but I found that theres no cost basis for any of them.The problem is, the account is with Schwab, but it was originally bought under Smith Barney, which is now Morgan Stanley, so the whole thing is kind of a mess. Ive tried calling all the different institutions, but none of them have any record of it.So, ok, fine, Ill just estimate it myself. But the first stock I look into, ATT, apparently had several mergers and name changes in the past two decades, and Im not really sure how much of that is relevant. Basically, Im in way over my head here, and Im wondering if any of you guys have any suggestions.  <response>: Yahoo has historical stock prices adjusted for splits and dividends.See, e.g., 