It was launched in 2005 but it remains a paltry, undernourished thing. It's the National Park Service's Sesquicenennial website. Event news: absent. Press releases: none. Calendar: none.
If the Sesquicentennial is going to have a national (or federal) character at all it will clearly be not through some national commission doing stuff. The only hope for a national commemoration now is via the NPS staging events at its sites countrywide.
Right now, that does not appear likely, if this website is any indicator.