The Visitor Center/Museum is open from 9am-4pm Wed-Sun. The Visitor Center/Museum is closed Mon-Tues. The trails and park grounds are open all week.
Whitman Mission National Historic Site's visitor center/museum is open from Wednesday-Sunday 9am-4pm. The visitor center is CLOSED Monday-Tuesday. The grounds, paths, and trails remain open to visitors seven days/week.
To view the park film: https://www.youtube.com/watch?v=oFLsOEnKMg0