It's Thursday, Sept. 20, National Pepperoni Pizza Day. Happy birthday to 'Game of Thrones' author George R.R. Martin (1948). Today in 1806, the Lewis and Clark Corps of Discovery arrived at the frontier settlement La Charette, Missouri, on their return trip from the Pacific Northwest. They left two years earlier. Expect some rain showers with a high in the low 70s. Here are a few things to do while you're waiting for your pizza today:

• Hear PSU students' ideas about the future of Hillsboro Airport during a presentation at the Multnomah Athletic Club, 7:15 to 9 a.m., 1849 S.W. Salmon St. www.portofportland.com

• Honor firefighters lost in the line of duty at the 13th annual Oregon Fallen Fire Fighters Memorial, 1 p.m., Oregon Public Safety Academy, 4190 Aumsville Highway S.E., Salem. www.oregon.gov/DPSST/FC/pages/fallenfirefightermemorial.aspx

• Hear Portland author Ann Smith read from the second edition of her book "100 Things to Do in Portland, Oregon, Before You Die," 2 p.m., Portland State University, 1715 S.W. Fifth Ave. www.awordsmithcomm.com

• Meet singer/songwriter John Prine and have him sign his latest album, 4 p.m., Music Millennium, 3158 E. Burnside St. www.musicmillennium.com

• Party with the National Multiple Sclerosis Society at its annual Gala MSfundraiser, 6 to 9 p.m., The Nines hotel, 525 S.W. Morrison St. www.nationalmssociety.org/Chapters/ORC/Fundraising-Events/Gala-MS