Search your local library for books on the history of New Mexico. Read New Mexico Magazine online at Nmmagazine.com, a magazine dedicated to the state's history. Check out websites on the history of New Mexico such as Newmexicohistory.org and Free.ed.gov. These sites may have information and perspectives unavailable in other sources. Build a good background knowledge using these sources.
Lay out a pre-Mexican War map of the United States that shows the country before New Mexico was a U.S. territory. Your students will see that the land belonged to Mexico at that time, and your teaching of the history of the state can be built around its origins. The map will serve as a blank slate for your students to slowly fill in with every lesson.
Use the New Mexico History Museum website's Interactives feature at Nmhistorymuseum.org with your students. Available topics for interactive study are the Treaty of Guadeloupe Hidalgo, The Segesser Hides, Shifting Boundaries and The Threads of Memory. The interactive programs are in-depth studies that allow for analysis of historical documents and maps, and provide lesson plans and teacher-specific assets.
Visit the Federal Resources for Educational Excellence website's New Mexico section at Free.ed.gov. Here you will find a collection of articles and links for educators along with interesting ways to approach each topic.
Arrange for a trip to the New Mexico Museum if your class is within easy distance of Santa Fe. A visit to the museum would be a culmination of their study.