The archaeology museum run by the Universidad Nacional de Trujillo is the best place to understand the chronological sequence of cultures that occupied this stretch of the Peruvian coast — from the earliest Cupisnique and Salinar traditions through the Moche, Wari, and Chimú to the Inca. The collection spans ceramics, textiles, metalwork, and bone tools.
It's a good first stop before visiting the major sites outside town, especially the Huacas del Sol y de la Luna, as it gives you the cultural framework to make sense of what you're seeing. The museum is located near the Plaza de Armas in the colonial centre.