Let $A$ be an $r \times n$ matrix of rank $r$ over a valued field $K$, and for each $r$-subset $B \subset \{1,\dots,n\}$ let $p(B)$ be the valuation of the maximal minor of $A$ using columns in $B$, with $p(B)=\infty$ when the minor is zero. Then $p$ is a valuated matroid.