There are a number of sources for stock prices, some that will be easier to find locally than others. There are also titles that are good for obsolete securities in our Business History: A resource Guide.
Newspapers may be the most accessible resource for most people. They won't be useful for someone who needs many dates or a range of dates that spans a large amount of time, but they are good for those who need a few days. If a local paper did not publish their own listing of stock prices, big city papers often printed the closing prices and those papers may be more accessible.
Sometimes these papers may be in microfilm but there are databases like Proquest Historical Newspapers, Newspapers.com, and NewspaperArchive have digitized newspapers. If you are using a database take advantage of the database indexing to limit results and don't search on the company name because papers often listed companies by a shortened and abbreviated name. Search on the exchange name and then look at the full list.
There are a few databases to get historical stock prices but accessing them may be a bit more difficult. The Library has access to Global Financial Data (not “all” companies are covered) and Factiva (only has a rolling 5 years). Other databases that the Library does not have that do have stock prices, are Bloomberg, S&P CapitalIQ, and Factset.
There are three individual titles for the three different exchanges - American, New York, and NASDAQ. This title may not be overly accessible but may be available in print or microfiche though a larger public library system or university library. The Library does have the titles in print in the Science & Business Reading Room near the reference desk.
Databases like Factset and the Bloomberg terminal have deep historical reach in terms of stock prices, but the Library doesn't subscribe to either. However, the subscription resources marked with a padlock are available to researchers on-site at the Library of Congress. If you are unable to visit the Library, you may be able to access these resources through your local public or academic library.
These titles from Standard & Poor's (S&P) give the daily prices of stocks for the three exchanges. Some libraries that do have this title may actually have this title in microfiche.