This summer I had the chance to visit the Pioneer Trail and bike the majority of its length. This was the second rail to trail conversion in Grundy County in the mid-1980's, after development of the Comet Trail in the Beaman-Conrad area. The Pioneer Trail extends from Holland to Grundy Center; and then you must travel east of Grundy Center by about a mile via highway where you pick it up again and can continue through Morrison, to about a mile west of Reinbeck where the eastern trail head exists. It mostly follows Highway 175 for this stretch.
The trail is well maintained and features a nice mix of wooded and open areas. In Morrison, you can jump off the trail and visit the Grundy County Conservation Board's mueseum and headquarters. There's plenty of eating and drinking establishments along the entire way.
Efforts are currently underway in Grundy Center to close the gap through the east side of town.