The UCSB Library DREAM Lab supports a number of tools for acquiring and analyzing social media data. Feel free to schedule a consultation if these guides do not answer your questions.
Extending back to 2010, and updated daily, the Harvard Center for Geographic Analysis (CGA) contains more than 10 billion tweets. Extractions require reimbursement to CGA.
NCapture is a free web-browser extension that allows you to quickly and easily capture content like web pages, online PDFs, Twitter tweets, and Facebook posts for import