The Gold Rush produced an incredible amount of gold, which caused the economy to boom, producing wealth of all sorts for the Pacific Coast. Gold deposits were extensive, meaning that no single person or group of miners were likely to become millionaires, but it was possible to "make a pile" in the vernacular of the day. A "pile" could be as little - or as much depending on your point of view - as $10,000. And that meant that you could return to the East or to the Midwest, buy a farm with livestock, and do very well for yourself.

Because the gold deposits were at or near the surface, it was easy for the gold fields to be picked over by the tens of thousands of 49ers who arrived. Within three years, it was becoming increasingly difficult to make a decent wage. I co-edited a collection of Gold Rush letters from the Grosh brothers, which provide an economic portrait of these sorts of 49ers. The brothers left Pennsylvania in February 1849, crossed Mexico, and arrived in San Francisco several months later. They and much of their company were so sick it took them two years before they were able to finally arrive in the gold fields. They were offered jobs in San Francisco, and they should have taken them since it would have set them up financially in a much better way. But they had gold fever, and they went to the mountains. Their daily wage was often about $2 per day when gold was selling for about $16 an ounce - meaning that the two brothers were retrieving about a quarter ounce a day. This barely met their needs and would not result in an accumulation of wealth. The brothers consequently sought underground deposits. They were correct in pursuing this goal because extensive mining was necessarily going to be replaced with intensive, underground mining pursuing veins of gold. But this game required expertise (and investment) and more luck since gold veins were rarer than surface deposits had been. Just as it seemed they might finally strike it rich (SPOILER ALERT), they both died in 1857.

The Grosh story answers your question: the Gold Rush continued, but depleted resources meant that miners realized declining rewards, and the hype correspondingly diminished. The real wealth to be made shifted from mining to the many other things that California had to offer. Gold Rush era fortunes had been made, but most often they were made by bankers and entrepreneurs who took advantage of the market represented by the tens of thousands of Argonauts who arrived with dreams and sought the wealth in the mountains.

For additional insight into this period using a primary sources, in this case the diaries of Alfred Doten, see /r/Doten.