Placer County runs between the Sacramento Valley and the Sierra Nevada mountains, against Sacramento County in the west and 100 miles east to Lake Tahoe. Along the present-day southern border, gold was discovered in 1848 by James Marshall at John Sutter's lumber mill, leading to the California Gold Rush. This relatively narrow county (only 10 to 15 miles across in some spots) has early immigrant trails, wagon roads, railways, and highways all passing through as they head across Donner Summit and across the Sierra Nevadas. Mining, agriculture, transportation, logging, and recreation made Placer County important in the past, and they keep it a thriving place to live now in the 21st century. Title: 'Placer County' author comes to town Author: Cheri March Publisher: Colfax Record Correspondent Date: 3/18/2010 Arthur Sommers knew he'd dig up old photos for his latest book. He just didn't expect to dig up a couple of mysteries. Sommers' name might sound familiar. The Auburn-born author and historian penned a book on Auburn for Arcadia Publishing's Images of America series in 2008, drawing on the thousands of photos and postcards in his own private collection. This time he's teamed with Arcadia for a more ambitious project. Released in January, "Images of America: Placer County" contains 200 photos and accompanying captions of cities and towns from Western Placer County to the foothills, from the Sierra to the Foresthill Divide. It also sets straight some historical errors. In Colfax, for instance, Sommers tackled the mystery of the moving monument. Near the Placer County border, he solved the mystery of the missing town. Sommers will sign copies of "Placer County" from 1 to 3 p.m. Saturday at the Colfax Heritage Museum. It's his way of saying thank you to the Colfax Area Historical Society, one of several groups that helped the author set the record straight. "The first book on Auburn - that was easy," said Sommers. "Every picture was of Auburn. Every piece of information was about Auburn. But (this time) I was looking at Lincoln, Roseville, Loomis and I needed a lot more help." Few Colfax residents are aware that a Nevada County Quartz Monument existed, since it was torn down possibly in 1920. Newspapers and history books tell the story. But the problem is, they often tell it wrong. Nevada County began construction on a rock monument - complete with fountain - in 1907. Many pictures show the sturdy structure in downtown Colfax, across the street from the railroad tracks, and many people assumed it was built there. But Sommers confirmed through photos that the monument was originally built 25 yards away between the Southern Pacific and Nevada County Narrow Gauge railroad tracks, below the Colfax Hotel and next to the Colfax railroad depot. This made sense, considering its purpose was to promote the nearby county to train travelers. "The idea was that people might see the monument and decide to get on the narrow gauge railroad and go to Grass Valley," Sommers said. In 1914, the monument was moved when workers realigned the tracks. During his research, Sommers often came across an early-20th Century photo of a Colfax crowd gathered by the tracks. Captions usually stated the people were waiting for President Theodore Roosevelt, who paid a visit to Colfax via train in 1903. But the monument visible in the photo's corner says otherwise. "I knew the Quartz Monument wasn't built until 1907," Sommer said. "The people aren't waiting for Teddy Roosevelt's train. They're waiting for the monument dedication." One of the first photos in "Placer County" features a one-room schoolhouse in Riego, a tiny town west of Roseville. That photo - and the town - almost didn't make it into the book. While everything Sommers read in print placed Riego in Placer County, online information advised the town fell within Sutter County borders. Bothered by the ambiguity, Sommers contacted local assemblymen, libraries and historical societies. But no one could verify the town's official location. Finally, an e-mail to the U.S. Geological Survey shed some light. Though people who live in Riego were counted as Placer residents, a virtual marker had placed the villa - which happens to be located on a small southwest peninsula - in Sutter County. Within 72 hours, USGS had amended its database, giving Riego a permanent place in Placer - though its airstrip remains across the border. "All that time for one paragraph in a caption," Sommers said. "There are 220 pictures and each picture needs its own little story." Thanks to Sommers, the real stories of Placer County are finally being told." Arthur Sommers received his bachelor of arts in history from San Francisco State College in 1972. After spending the subsequent 25 years working for the Department of Defense, he returned to his love of history and has been collecting old Placer County photographs since retiring in 1999. In 2008, Arcadia published his b