The element phosphorus is major part of a suite of biologic elements that make up life, with the others including carbon, nitrogen, oxygen, hydrogen, and sulfur. Phosphorus is unique in this list in that it ultimately must have come from a mineral source. We review here the reasons why phosphorus has such a prominent role in modern biology and the likely timing when phosphorus first became critical to life, including at its origin. Using the suite of phosphorus biomolecules that are common to all known life, we argue that several types of molecules should be seen as specific targets of prebiotic chemistry research. We review the routes to synthesizing these molecules, including the use of activated organics and phosphates, and non-aqueous solvents. We find that routes involving activated phosphates and semi-aqueous solvents may have been likely environments where the first phosphorylated molecules may have formed.