How do I find an old insurance company named Sun Life Insurance Company of America located in Baltimore MD?

Before an insurance company can sell insurance in a certain state, it must register with the State Dept of Insurance. If the company is sold, then it must notify the Dept of who it was sold to. If it just closes down, its policies were likely sold to another company, the Dept will have to be notified of that as well.

Contact the MD Dept of Insurance and inquire there.

I found 2, 50 year policies. After calling around, I found that Sun Life is now Monumental Life Insurance Co. 800-638-3080.