Jacobs grew up in Michigan, where he studied law. He emigrated to Oregon Territory in 1852 and later settled in Seattle. He was appointed associate justice of the Washington Territorial Supreme Court in 1869 and was named chief justice a year later. He was reappointed chief justice in 1874. That same year, he was elected as a territorial delegate to the U.S. Congress and then re-elected for a second term two years later, serving from December 6, 1875, to March 3, 1879.
After completing his term as Seattle's mayor, Jacobs continued to be active in both territorial and municipal affairs. He was a member of the Washington Territorial Council from 1885 to 1887. He later served as corporation counsel for the City of Seattle (1890 to 1892) and as a Superior Court judge (1896 to 1900).
One of Jacob's more public acts was the delivery of a eulogy for President James A. Garfield (whom he had known) during a memorial service for the president in Seattle on September 27, 1881. Between 3,000 and 4,000 people attended the memorial, in one of the largest gatherings in Seattle at that time. Garfield died on September 19, 1881, 80 days after being shot by an assassin.