EXHIBIT 21.1 SUBSIDIARIES OF ST. MARY LAND & EXPLORATION COMPANY A. Wholly-owned subsidiaries of St. Mary Land & Exploration Company, a Delaware corporation: 1. Nance Petroleum Corporation, a Montana corporation 2. St. Mary Energy Company, a Delaware corporation 3. Four Winds Marketing LLC, a Colorado limited liability company 4. Agate Petroleum, Inc., a Delaware corporation 5. SMT Texas LLC, a Colorado limited liability company B. Other subsidiaries of St. Mary Land & Exploration Company: 1. Box Church Gas Gathering LLC, a Colorado limited liability company (58.6754%) 2. Trinity River Services LLC, a Texas limited liability company (25%) C. Wholly-owned subsidiaries of Nance Petroleum Corporation: 1. NPC Inc., a Colorado corporation D. Wholly-owned subsidiaries of St. Mary Energy Company: 1. SMEC Texas LLC, a Colorado limited liability company E. Partnership interests held by St. Mary Land & Exploration Company: 1. Hilltop Investments, a Colorado general partnership (50%) 2. Parish Ventures, a Colorado general partnership (100%) F. Partnership interests held by SMT Texas LLC: 1. St. Mary East Texas LP, a Texas limited partnership (99%) (the remaining 1% interest is held by St. Mary Land & Exploration Company) G. Partnership interests held by SMEC Texas LLC: 1. St. Mary Energy Texas LP, a Texas limited partnership (99%) (the remaining 1% interest is held by St. Mary Energy Company)