It looks like there were between 200,000 and 500,000 people who showed up at the two protests in Washington DC and SF. Although the official police estimates put the combined total at 100,000. Photographs and videos available on many web sites show that there were clearly many, many, more people than that.
“Police did not quarrel with the organisers’ estimate of 500,000, though that seemed excessive. Certainly, there can hardly have been less than 100,000… [In Washington D.C.]
…There were protests in San Francisco (organisers’ estimate: 200,000 people; police estimate: 55,000) and in smaller cities, most of them as frigid as Washington, across the country.”