The stand-off came amid tensions in the city over the fatal stabbing on a train of two men who tried to help teenagers apparently targeted by racial abuse.
A suspect, Jeremy Joseph Christian, is accused of murder.
The 35-year-old is due to appear in court on Wednesday.
Bottles and bricks
Sunday's rival demonstrations were at one point separated by police using pepper spray outside Portland's city hall.
The confrontation was mostly peaceful, although bottle and brick were thrown, police said.
At least 14 people were arrested, mostly those taking part in the anti-Trump protest.
The president tweeted last week that the stabbing attacks were "unacceptable".
The attack unfolded on 26 May after Mr Christian allegedly spewed "hate speech" towards two young women on a train, police said.
Taliesin Namkai-Meche, 23, and Ricky Best, 53, intervened and were fatally stabbed, investigators said.
Another man, Micah David-Cole Fletcher, was slashed in the neck and is recovering.
Destinee Mangum, 16, said she had been with a friend wearing a hijab on the first night of Ramadan - Islam's holiest month - when the suspect targeted them.
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