SALT LAKE CITY — Another Pioneer Day celebration goes in the books this weekend — that's 174 Utah birthdays if you're keeping score — and for the Sons of Utah Pioneers the festivities mean another significant addition to their clubhouse in Salt Lake City. Already full of pioneer-era artifacts, from Avard Fairbanks sculptures to hundred-year-old oil paintings to the best collection of trek diaries this side of the official archives of The Church of Jesus Christ of Latter-day Saints, the Sons of Utah Pioneers headquarters building near the mouth of Parleys Canyon took possession this week of a hand-painted American flag that's even older than Pioneer Days.