Here's where you can get the mailing address for a Federal Form 1040X if you live in Maryland. The Maryland amended return should have the address on it near the signature section.
At the following article, find the 1040X in the table and choose the column based on whether a payment is enclosed or not.
https://www.irs.gov/uac/maryland-where-to-file-addresses-for-taxpayers-and-tax-professionals
