The late senator's casket arrived at San Francisco's City Hall shortly after 8 a.m. with an honor guard accompanying the late senator's remains.
The senator's family arrived shortly after.
Among those saying their farewells was Speaker Emerita Nancy Pelosi.
Pelosi remembered a resolute Sen. Dianne Feinstein, who still managed to show her gentle nature.
"I was thinking of the words during the night about how gentle she was but how strategic she was," said Pelosi. "She knew her purpose and she did things on her own terms, but she always did them with gentleness."
Feinstein served as the city's first female mayor from 1978 to 1988, a seat now occupied by London Breed, who reflected on the senator's lasting impression on the office and the City of San Francisco.
"We have, you know, had guests and people come up, her stature is upstairs," said Breed. "Flowers have been pouring in, and you still feel her presence because of how actively engaged she was."
A procession of city workers in uniform, staff and friends of Feinstein made their way past her casket and into the south light court where they signed condolence books.
"Working for her was just the privilege of a lifetime," said former staffer Abby Ellis. "She governed and thought about public service in a way that I think you don't see anymore in politicians."
Those whom she mentored said she always expected the best out of her staff and always made time for them.
"You know I worked for her almost 20 years ago, and she's been a mentor, and we've kept in touch that entire time," said former staffer Ahmad Thomas.
"Checking on my wife and my kids, sending thoughtful notes. Always there for mentorship and advice."
The public began lining up long before the doors opened at 9 a.m. saying even if they didn't personally know the late senator, she had an impact on their lives.
"I just felt like it was my duty as a citizen to come and pay my respects," said Terry Webber.
"The work that she'd done is so wonderful, and she's truly going to be missed," said Lajuana Washington. "You know, she's really going to be missed. I just really loved her and inspired her a lot."
Mourners will be able to come by City Hall and pay their respects throughout the day until 7 p.m. The senator is set to be laid to rest Thursday.