If the students hate it, then the exercise isn't going to work, so the first concern is whether students liked the Trails.

They did. They told me this in comments, but they also demonstrated it by actuallyl doing the exercise. They liked going off on their own to explore, and they liked coming back to the group with their findings.

The most obvious benefit is that students learned historical information. That's the point of the course, after all. What they learned was unpredictable, as they are free to choose the topic, but whether this topic or that one is chosen in a given semester is not important to me.

Because of the nature of web-based discussion, not only did the individual student learn, all the rest of the students learned as well. This was valuable. Students weren't merely finding out information, they had to explain what they found to their peers. This would be extremely difficult to do in a real-time course because the process is time-consuming, forcing the instructor to make hard choices between time spent on lecture and time spent on discussion and time spent on student presentations. This obstacle does not exist in the asynchronous classroom.

No one said this, but I think they liked the informality. They have to do papers, which are formal exercise (and are rather like trails in themselves). But this exercise is informal. It invites opinions and reactions, and includes shared discovery and community. Papers are impersonal; trails are personal.

One telling bit of evidence supporting this conclusion is that students almost instinctively tried to stay off each other's Trails. When they discovered that a Trail they'd explored had already been done by someone else, their disappointment was palpable. Here was no spirit of cooperation, nor yet of rivalry; rather, it was a spirit of exploration, a natural human desire to find something not found by others and to tell of one's discoveries.

Students learned to use search engines. They learned of new ones, and they learned of different approaches to them.

Students were introduced to the evaluation of sources in a fairly pragmatic way. This is a topic I press harder in my upper division courses, but an introductory course is an excellent place to introduce students to the concepts. With my particular discipline, we can take up topics such as the plethora of K12 sites, material provided by prejudiced sources, and the treacherous ground of the enthusiastic amateur.

Another benefit to the students is that it gives them something that belongs to them. A not-uncommon comment from students who under-participate is that they feel intimidated by the level of conversation. Everyone else, they say, seems to know what they are talking about. Another form of this sentiment is that the student feels everything has already been said or asked. But a Trail is the student's own. There will always be unexplored Trails, so the student can always cover ground no one else has covered.