Question RE Cost Basis of Inherited Primary Converted to Rental

[Bradley Chapple]

My wife inherited some property waaaaaaay back in 1994 when the home was worth next to nothing (let's say $75k, for the sake of putting a number on it). It became her primary residence for a very long time.

Fast forward almost 30 years and the house is worth $400k+. We recently moved, turned the home into a rental, and refinanced it to a 30-year fixed.

My accountant recently requested the value of the home in 1994 to establish the cost basis for depreciation purposes.

This doesn't seem right to me. Although I'll readily admit that I know very little about this stuff, I always assumed the cost basis would be based on the value of the property at the time it was placed into service, not the time that it was originally acquired. Am I missing something? Why would the original value at the time of acquisition be needed? Does this value get plugged into a formula of some kind to establish the cost basis, or does the value of the property in 1994 ($75k) become the cost basis?