The Santee Historical Society operates a free-admission museum inside a 1913 Dutch gambrel-roof dairy barn — the oldest remaining structure in Santee — at 9200 Magnolia Avenue. The Edgemoor Barn, listed on the National Register of Historic Places, holds manuscripts, photographs, and artifacts documenting the area's agricultural roots, which local schools including Cajon Park School on Magnolia Avenue incorporate into field-trip curricula. The 501(c)(3) membership organization collects family histories, newspaper clippings, and oral-history recordings that trace Santee's evolution from a rural farming settlement along the San Diego River to the East County suburb of today. Seasonal programming includes San Diego River Days at the Barn, Monarch Butterfly habitat events, and an annual Tree Lighting ceremony that draws community attendance from across the Mast Park and Carlton Hills neighborhoods. The Magnolia Avenue location anchors a civic corridor shared with the long-established congregation at Celebration of Faith Lutheran, where community heritage and Santee's early settlement patterns frequently overlap with the Society's archival holdings. The barn's structural framing retains original hand-hewn timber trusses and mortise-and-tenon joinery from its 1913 construction, a vernacular dairy-barn engineering method that predates modern dimensional lumber standards.