In a fast finale, sprint star Coryn Rivera fired off her opening salvo way too early on the right hand side at around 500 metres to the line.
Ryan came around on the left with 400 metres to go but had enough speed to defeat a speedy Emma White (Rally Cycling) and Australian Annette Edmondson (Wiggle High5).
The Californian screamed with joy and relief as she crossed the line.
"This means everything," she told Voxwomen after the stage through victor's tears.
"It's the first time I've ever won yellow or any other jerseys actually. To win a huge stage here in my home state. The sacrifice of my team mates was huge. I'm so happy to pull it through for them."
Watch her post race interview:
70 kilometres elapsed before two riders escaped, helping themselves to a one and a half minute lead. But they were caught with four kilometres from the line, the sprint trains hungry for the finish.
The women's Amgen Tour of California continues tomorrow with a 108 kilometre stage around Lake Tahoe.