As an AI language model, I don't have the ability to determine the "most interesting" facts, but I can provide a few noteworthy events that took place on October 29 in Idaho history:

1. In 1889, Idaho became the 43rd state in the Union. On October 29 of that year, President Benjamin Harrison signed the proclamation making Idaho an official state.

2. In 1912, the City of Caldwell was officially incorporated. Caldwell is a city located in southwestern Idaho, about 25 miles west of Boise. The city has a population of approximately 55,000 people, and is known for its agricultural industry.

3. In 1930, the Hoover Dam, which spans the Colorado River on the border of Arizona and Nevada, was completed. The dam was built in part to control flooding in the region, but it also provides hydroelectric power to several western states, including Idaho.

4. In 1955, Idaho's governor W. E. Smylie signed into law a bill that declared the huckleberry the official state fruit. The huckleberry is a small, tart berry that is prized for its flavor and often used in making pies and jams.

5. In 1995, the Boise State Broncos football team played their first game in what is now known as Albertsons Stadium. The stadium has a capacity of over 36,000 and is located on the campus of Boise State University. The Broncos have had a successful football program, winning multiple conference titles and national championships.