Less than a year after launching its Shopping Express service in Silicon Valley and San Francisco–delivering retail products straight to homes on the same day they're ordered online–Google is muscling even farther into Amazon's territory, offering overnight delivery across Northern California.

The search-giant-turned-internet-retailer announced the move on Tuesday. As with its same-day delivery service, which recently expanded to include parts of Los Angeles and New York, Google isn't building Amazon-style warehouses to fill with its own inventory. Instead, orders will be filled by chain stores such as Target, Walgreens, Staples, and Whole Foods.

When Google started offering same-day delivery to the public last September, it felt more like a curiosity: With all its algorithmic, artificially intelligent might, what could Google possibly pull off in the physical world? But in expanding its range regionally and promising Amazon Prime-like delivery speeds, Google seems to be moving toward becoming a more conventional e-commerce competitor to Amazon. It's a move that's about money. If Google can actually deliver goods, maybe it can give shoppers a better reason to start product searches on its site instead of Amazon's. The more shoppers Google attracts, the more incentive its advertisers have to keep buying ads.

The overnight service is available today in cities on the other side of the bay from San Francisco, including Oakland and Berkeley. Google says the service will expand over the next few months as far north as Crescent City along the Oregon border and south to Fresno and California's Central Valley. In its blog post, Google calls out Big Sur and Yosemite as two prized wilderness destinations that will also be within the reach of its deliveries, which the company says will be brought by "major shipping carriers." Google promises that any orders placed by 7:00 p.m. the night before will be delivered the next day.

By spreading its reach out beyond cities, Google is putting its point-to-point version of delivery to a much broader test. Amazon has perfected the art of shipping orders quickly from massive, centralized facilities. Logistics experts have questioned whether a decentralized model that uses retail stores designed for shopping can really work as substitutes for warehouses designed for shipping. But ultimately logistics is a math problem, and math is something Google is really good at.

Google is also likely continuing to seek ways to test out its growing fleet of self-driving cars. In an interview with The New York Times' John Markoff, Google co-founder Sergey Brin didn't rule out the possibility of using its new pod-shaped prototype vehicles for deliveries. But there's a mundane problem, Brin conceded, that neither Google nor anyone else is close to solving: "The problem with the Google Express stuff," he said, "is there is still the dude who gets out and puts stuff on the porch."

Correction 6/3/2014 6:20 PM EDT: An earlier version of this story said that Google's new overnight service would make deliveries using "company couriers." Google says the service will actually work with "major shipping carriers."