From the Ohlone and Mission periods of the 18th century through the agricultural era of the Valley of Heart's Delight into contemporary Silicon Valley, a pictorial history of Santa Clara County is taking electronic form.

A coalition of private and public organizations is assembling, digitizing and posting online thousands of images that offer a glimpse into life in the Santa Clara Valley over the past few centuries.

Called Silicon Valley History Online, the program takes viewers, mouse click by mouse click, on an exploration of the valley's cultural diversity, immigration, agriculture, commerce, education, technology, transportation and urban life.

``This is a gateway to Santa Clara County's past,'' said project director Paula Jabloner, senior archivist of History San Jose, the historical organization that manages the city-owned Historical Museum and the Peralta Adobe-Fallon House.

The easy-to-navigate Web site, www.SiliconValley History.org, was unveiled Thursday at the Dr. Martin Luther King Jr. Library in downtown San Jose.

Click on the site, and you get a picture of San Jose's castle-like City Hall in 1854. Another click, and you're looking at a triple-deck excursion boat in Alviso in 1895. Click again and see the pilots of the first San Jose to San Francisco airmail route in 1925.

The list goes on and on.

It's starting small with about 80 images on the site. By August, the project hopes to have 1,000 pictures stored; by 2006, Jabloner said, organizers want to add 6,000 more from the archives of the participating organizations.

``We encourage you to go back frequently and see what's new,'' Jabloner said during the demonstration in the library's fifth floor Special Collections Room, which houses a wealth of artifacts about California's history.

``This is an innovative window to the past,'' said San Jose Mayor Ron Gonzales, who attended the demonstration. ``We need to find more ways to connect our past with our future.''

Gonzales said this is his favorite time of year because it reminds him of his childhood, when the valley was ``orchards and orchards.'' When the sea of fruit tree blossoms was viewed from the hills, he said, ``it looked like it snowed here.''

New arrivals to Silicon Valley ``have no clue about our past,'' Gonzales said. The history project ``has the ability to connect a community with that knowledge. When people have access to knowledge, they want more knowledge.''

The project includes photographs, postcards, manuscripts and other materials related to Santa Clara County's history that are archived at seven libraries and museums in Santa Clara County.

A year ago, those institutions obtained a $144,000 grant from the U.S. Institute of Museum and Library Services in Washington, D.C., to launch the online project. Similar projects have been done by other institutions across the country.

The local participating organizations are History San Jose, Santa Clara University archives, San Jose State University Special Collections Department, California History Center at De Anza College, the Intel Museum, San Jose Public Library California Room and the Santa Clara City Library Pavilion Room.