Millions of Americans flooded government websites Tuesday to get a long-awaited look at insurance options available under the Affordable Care Act, but the high traffic contributed to widespread computer problems on what President Barack Obama hailed as a historic day.

HealthCare.gov, the federal Internet marketplace serving more than 30 states, was jammed for most of the day, with people encountering error messages that froze their applications.

In states operating their own marketplaces, the experience was spotty. Maryland's site, Maryland Health Connection, was down for the morning and sluggish into the evening. Lesser problems were reported in Colorado, Washington, Hawaii and elsewhere.