The ISP says it decided to restrict service this way after receiving numerous calls from customers concerned about censorship.
The customers' requests for firewalls preventing access to these sites followed the tech giants' decisions to close down Donald Trump's accounts and suspend his activity.
After the decision started attracting attention on social media, the owner of the company said the websites would only be blocked for customers who asked.
KREM.com notes that Your T1 WIFI "may violate Washington state's Net Neutrality law, which states that internet providers may not manipulate access to content."
jasonbuechler writes: A North Idaho internet provider, Your T1 WIFI, emailed customers to say customers would need to opt-in to access Facebook and Twitter from its service.