>>> good evening. this was a dark day for the nation's fnz and for millions of americans with a financial stake in the markets. the very same americans who are still processing the fact that our country has lost its top credit rating. here's the damage from today. the dow down over 634 points. that's the sixth largest point drop in its history. the worst since '08. nasdaq lost just about 7% of its total value. s&p 500 lost 6.6% of its value in one day. the president went on television at midday to reassure americans but the damage was done. the markets continued to drop while he spoke and the damage continues. it is a bigger systemic problem with no real end in sight. we begin our coverage tonight with cnbc's maria bartiromo. she's at the new york stock exchange. maria, you won't see many days like this one in your lifetime.

>> reporter:  it is true, brian. what day today on wall street after last week's sell-off and the credit downgrade by standard & poor's late friday. anxieties mounted over the weekend and all eyes were on wall street this morning. stocks dropped right at the opening bell on wall street as the selling that started thursday just kept going. not a single stock on the s&p 500 ended in positive territory.

>> that's really bringing the market into the red.

>> there is concern that the s&p downgrade may do something to consumer confidence and thereby ease us a little closer to the infamous double dip that everybody is worried about.

>> good afternoon, everybody.

>> reporter:  president obama came out to reassure investors.

>> this is the united states of america. no matter what some agency may say we always have been and always will be a aaa country.

>> reporter:  while the markets sold off another 400 points after the president's speech, sales of u.s. treasuries remain strong, easing fears that interest rates might rise and mortgages cars and student loan ares.

>> if the world say risky place and investors shed risk, they're not going to shed the least risky asset, still u.s. treasury securities.

>> reporter:  in an attempt to avoid a recession in europe, the european central bank bought bonds to keep spain and italy afloat but that may not be enough.

>> there is going to be a bigger burden on france and germany. the question is, do they have enough money -- do they have the will to bail out the other countries?

>> reporter:  some investors sought safety in gold, sending gold prices up more than $61 to a new record high while oil closed just above $81 a barrel.

>> look around. investors are being turned off.

>> reporter:  despite the chaos, dan arbis sees one possible advantage to the downgrade.

>> some day we will thank the s&p for the downgrade. it is a message to washington, we must begin to address the long-term solvency of the united states of america.

>> reporter:  next big event to watch, the federal reserve will meet tomorrow in its regularly scheduled meeting and investors will be paying close attention to see if the fed says anything about the economy and whether it requires additional stimulus right now, brian.

>> maria bartiromo starting us off from the floor of the exchange. maria, thanks.