At least 268 of 534 lawmakers currently elected to the House of Representatives and the Senate had a net worth of $1.0 million or more in 2012, according to disclosures filed by all members of Congress.
For a few, that figure went into the hundreds of millions -- and the median net worth was just over a million, at $1,008,767, according to analysis by the Center for Responsive Politics at OpenSecrets.org.
Median figures for Republicans and Democrats in the "millionaires club" are nearly equal, with Democrats edging just a bit ahead with $1.04 million compared to $1.0 million for Republicans.
But in both parties, the average has risen from a year earlier, from $990,000 for Democrats and $907,000 for Republicans. That year, some 48 percent of lawmakers were in the millionaires club.
According to the Center for Responsive Politics' analysis, the wealthiest Congressman was Representative Darrell Issa, a Republican from California, who made a fortune with a car alarm system he created. They calculated his net worth as averaging $464 million during 2012.
His least wealthy colleague was David Valadao, also a Republican from California, whose net worth was in the red -- a negative $12.1 million -- thanks to debts related to his family dairy farm.
"Members of Congress have long been far wealthier than the typical American," the center said, but noting a majority of "millionaires represents a watershed moment at a time when lawmakers are debating issues like unemployment benefits, food stamps and the minimum wage."
Even as polls "show how dissatisfied Americans are with Congress overall," said center director Sheila Krumholz, "there's been no change in our appetite to elect affluent politicians to represent our concerns in Washington."
She said it was "undeniable" that wealth is necessary "to run financially viable campaigns."
"And the most successful fundraisers are politicians who swim in those circles to begin with," she added.