Dad passed away in 2017, what tax forms need to be filed for MD and IRS?

You need to file his final 1040 with the IRS and his final state return with Maryland.

If Social Security has been notified, you can even e-file on his behalf.

For more information, follow these links: 

IRS on Deceased Taxpayer

E-file Deceased Tax Returns

https://turbotax.intuit.com/tax-tips/family/death-in-the-family/L5albFXM4

I am sorry for your loss.