There are two sites that maintain the share price history of the funds.

1.) TSP.gov — https://www.tsp.gov/fund-performance/share-price-history/

2.) TSPTalk.com — https://www.tsptalk.com/tracker/tsp_fund_price.php

You can copy & paste the above links in your browser.

The 1st table is 'to the best of our knowledge' reliable and automatically updated by the Federal government.

The 2nd table is internally linked to the TSP.gov site.