Even if it was held for investment purposes, say for it's potential to appreciate in value, unless it had some income-producing component such as a rental, then there would be no depreciation allowed.
The classification really boils down to intent. I'm curious how carrying costs on the property handled? If capital property, was the election made to capitalize the carrying charges, and were the elections to do so included with the 2017 and 2018 returns? Were those carrying charges expensed?