My profile picture shows me carrying backpacking gear and my older daughter, somewhere between 16 and 18 months of age at the time. We were heading out on a three day trip in the Sawtooths (Idaho), which included a pass at about 9500 feet. I was a few months pregnant, so we only did about six miles a day. The only real challenge was that she had recently stopped breastfeeding, and wouldn't drink formula or powdered milk. I carried fresh milk for her the first day, and we were back at the trailhead by noon on the third day, with milk waiting in a cooler. The middle day, we were able to keep her hydrated with water, but she really wanted milk, especially at bedtime. Other than that, we were all very happy campers. She loved wading in the sandy-bottomed little springs that flowed into Toxaway Lake, watching for squirrels, jumping off rocks, rearranging the sticks and pine cones, getting dirty. My own childhood was the same, hiking with my dad and grandma as soon as I could walk. I know a guy from another forum who takes his kids on little backpacking trips several times a year. He has six kids, and the oldest one is seven years old (a few of them are adopted, so most of them are four or five years old). I'm amazed that he can pull it off, but they always have a good time. Every parent has to stay within their own comfort and skill level, but really, there is no age limit if the parents are competent in the woods.