Well, all the Web pages using Google maps to display information about Mt. Rainier NP are updated with the NP boundary identified as a blue line. The boundary incorporates the original 1899 designation, the 1933, 1987 and 2003 additions, the last being the small exclave of land outside the Carbon River entrance in the northwest corner.
This land was approved by Congress and signed by President Bush in 2003 but took years to get the agreements for the exchange of land between the land owners and the NPS. The intervening land between the Carbon River entrance and the new NP land is under the USFS ownership so it will be protected for visitors to the NP.
So, if you encounter a map without the NP boundary, a boundary that looks obviously wrong, or just have questions about the NP boundary, please ask or let me know via e-mail.