The #ProtectMueller protests began just hours after the country's acting attorney general was announced.
Thousands turn out at US protests in support of Robert Mueller
Thousands of Americans took to the streets in cities and towns across the country on Thursday to protest the looming threat against special counsel Robert Mueller.
The protests sprang out of the White House decision to hire Matt Whitaker as acting Attorney General in the wake of Jeff Sessions' requested resignation from the post on Wednesday.
In response to Mr Whitaker's hiring, activist group Move On sent out alerts to its supporters, asking them to protest in their local areas. Before long the hashtag #ProtectMueller was trending on Twitter in the United States.
Many on the streets on Thursday evening said they felt Mr Mueller's investigation into Russian election meddling could be in danger under Mr Whitaker's leadership of the Attorney General's office.
These ideas are not without some backing. Mr Whitaker has been an outspoken critic of the Russia investigation, saying Mr Mueller had gone too far, and he is unlikely to recuse himself from the investigation. Critics say that with Mr Whitaker in charge, concealment of indictments or cutting of funding for the probe is possible.
Demonstrators posted pictures and video on social media showing small protests numbering in the tens up to larger ones with thousands of participants gathering in New York's Times Square.
Caroline Metzger, a retired teacher, went out to share her feelings on the issue in Mercer County, Pennsylvania. Her activism began with the Women's March in 2016, and has continued throughout Trump's presidency with her membership of activist group Indivisible.
"Trump is a danger to America and I won't sit by and let him win," the 67 year old told The National."
Wendy, 53, took to a busy main road in Northern Virginia with her 20-year-old daughter Cierra to raise awareness of Trump's "terrifying" hire.
"We are disgusted by what is happening to our country under Trump’s administration," she said.
"We were there because it’s something we can do and every act, big or small, matters right now. If even one person driving past us saw the hundreds of people on the side of the road with signs and felt less distraught knowing that there are more people who share their beliefs, it was worth it."
Shawn Kinzel-Auer, 43, said he protested in his home city of Minneapolis to show that no one is above the law.
"If Trump is innocent then the investigation will prove that conclusively...The US is a republic founded on the rule of law, not a tyranny or dictatorship. The President of the United States is merely a citizen elected to represent all of us."
Over in Texas, writer and editor Amy Hertz, 55, attended a protest in Houston with her local congressman Al Green. Comparing the current state of affairs to the Nixon Watergate scandal, she said it was important for traditionally Republican states to be seen speaking up.
"Houston is a strong progressive city. If we don’t show up our voices get overshadowed by the activities of cities in which everyone expects to see protests."
Mr Trump or the White House are yet to comment on the protests.