EXHIBIT 21 LIST OF SUBSIDIARIES OF MARTIN MARIETTA CORPORATION State or Percentage Country of of Securities Name of Subsidiary Incorporation Owned Martin Marietta Technologies, Inc. Maryland 100% Martin Marietta Materials, Inc. North Carolina 80.9% Martin Marietta Energy Systems, Inc. Delaware 100% Martin Marietta Investments Inc. Delaware 100% The subsidiaries contained in this listing are entities through which the Corporation conducts major activities. None meets the definition of a significant subsidiary under Rule 1-02(v) of Regulation S-X, however, considered in certain instances in a group of two or more entities or in the aggregate, as a single subsidiary, the subsidiaries listed above would constitute a significant subsidiary as defined in Regulation S-X. Martin Marietta has a number of other subsidiaries, but all of them, considered in the aggregate as a single subsidiary, would not constitute a significant subsidiary. Accordingly, the names of the particular subsidiaries are omitted.