The core WPF assemblies are:

WindowsBase.dll:- This is the core types constituting the infrastructure of WPF API.

PresentationCore.dll:- It defines numerous types constituting foundation of WPF GUI layer.

PresentationFoundation.dll:- It defines WPF control types, animation & multimedia support, databinding suport and other WPF services.

Besides these three libraries WPF also uses an unmanaged binary called milcore.dll which acts as a bridge between WPF assemblies and DirectX runtime layer.