The United Services Automobile Association (USAA) has been in existence since 1922 when 25 officers from the Army decided to band together to found the company. In fact, it started out as the United States Army Automobile Association. By 1923, the company began to offer affordable automobile insurance to members of other branches of the military. In 1931, 30,000 members of the armed services had set up policies through USAA. By the 1940's, the company recognized that service members overseas wouldn't have the time or means to renew their policies and set up an automatic renewal for them. If your father had a policy, USAA would have that information on file.
You don't supply any details about why you're asking this question. If you're hoping to learn if your father had a USAA policy, you need to speak with a USAA representative. You can reach USAA by phone, email, postal mail and on social media. To confirm whether you qualify for a policy, you must provide the rep with identifying and military details about him.
Please keep in mind that USAA eligibility requirements have changed quite a bit over the years since your father passed away in 1970. USAA requires that a member sign up their child for membership while still alive. If your father didn't help establish you as a member before his death, you can't become a member. That said, you can establish membership on your own if you are the spouse of a USAA member who set up membership prior to marriage. Widowers, widows and former spouses who haven't remarried can also apply for membership. If you're a current active member of the military or a veteran, you obviously fulfill the requirements for membership as well. With the retirement scenario, you must have received an Honorable discharge.