California's health insurance exchange said 144,178 people have newly enrolled in Obamacare coverage during the first month of sign ups.
During the initial rollout of the federal health law, 1.2 million people purchased a private health plan through the Covered California exchange.
State officials are trying to hold on to most of those existing policyholders during the renewal process now and add about 500,000 more to finish open enrollment Feb. 15 with 1.7 million consumers.
"The interest here in California remains strong," said Yolanda Richardson, chief deputy executive director at Covered California. "We look for the numbers to grow."
Richardson credited the state's increasing use of storefront locations run by certified insurance agents, clinics and other enrollment groups for boosting sign-ups.
She said there are more than 300 such locations statewide and consumers can find local help online.
Officials also reported that 216,423 people have joined Medi-Cal, the state's Medicaid program for low-income people, since Nov. 15. That's in addition to the 2.2 million who had already enrolled in 2014 as part of the health-law expansion.
Medi-Cal enrollment is open year-round.
This week, Covered California extended its deadline for Jan. 1 coverage and renewals to Sunday, Dec. 21. The cut-off had been Dec. 15.
Peter Lee, the exchange's executive director, said the state didn't grant the extension because of problems with online enrollment or long wait times -- which has been the case in the past.
Instead, he pointed to 157,000 people who have completed the application process but have yet to finish by picking out a health plan.
"The [information technology] systems are working great, but insurance is confusing," Lee said. "Many consumers signing up today are new to health insurance and we know they need help."
Another improvement this year is that many consumers are able to pay their first monthly premium online when using the state website.
Covered California and several of its participating health plans added that payment feature to alleviate earlier problems when people were left waiting weeks to get their first bill and confirmation of coverage.
Lee said that about half of the 144,000 new enrollees have already paid online.