I've read about this mysterious site in the middle of no where out in the Mojave desert. I've even drive right past it 4 times in the past couple years. Today I drove out to take a look, and there it was. A lone grave. The grave of Bonnie Keebler Harris who died in 1872. She was reportedly traveling a wagon trail and was buried here by her companions. The BLM station in Barstow has the original note that was found at the site years ago stuck in a bottle. It read "December 27, 1872, to whom it may concern: died this day of sickness; too far to travel so will put her here. Bonnie Keebler Harris, born December 1823 in New York, mother of five children. God rest her soul." The Mojave River Valley Museum has installed a permanent marker at the site.
Here's a Google map centered on the grave. It's only about 5 miles north of I-15 off the Afton Canyon exit (which is about 20 miles south of Baker). Current road conditions are challenging and the typical car will not make it through the deep sandy sections. In fact, my Land Rover was kind of swimming at times, where I'd estimate the sand was 8 to 10 inches deep. Last year the road was much easier and my MDX had no problems, but now I would strongly recommend 4WD and high clearance.