The Natural History Museum is the largest natural and historical museum in the western United States. It aims to inspire wonder, discovery and responsibility for our natural and cultural worlds with a collection that includes nearly 35 million specimens and artifacts and covers 4.5 billion years of history. General admission and programs are free to students, teachers and adult chaperones. Certain exhibits, such as the interactive Nature Lab and Butterfly Pavilion, require an additional registration — check the full list of exhibits for more information. Grade-specific guided programs are available October through January with an advance reservation. Teachers can also find lesson plans for self-guided visits on the NHM website. Visit requests should be submitted at least two weeks before the desire visit date. Reservations for the 2016-17 school year begin August 15.