Should I be receiving a 1099-S if I sold land I had for personal use in 2018?

Yes, it is appropriate that you would receive one. From the IRS:

Reportable Real Estate 

Generally, you are required to report a transaction that consists in whole or in part of the sale or exchange for money, indebtedness, property, or services of any present or future ownership interest in any of the following. 

1. Improved or unimproved land, including air space. 

2. Inherently permanent structures, including any residential, commercial, or industrial building. 

3. A condominium unit and its appurtenant fixtures and common elements, including land. 

4. Stock in a cooperative housing corporation (as defined in section 216). 

5. Any non-contingent interest in standing timber. 

Sale or exchange. A sale or exchange includes any transaction properly treated as a sale or exchange for federal income tax purposes, even if the transaction is not currently taxable. For example, a sale of a main home may be a reportable sale even though the transferor may be entitled to exclude the gain under section 121. 

https://www.irs.gov/pub/irs-pdf/i1099s.pdf