The route continues as a divided two-lane expressway in a more easterly, then southeasterly, direction as it crosses Tolay Creek and proceeds through the Napa Sonoma Marsh at the northern edge of San Pablo Bay.

SR 37 travels in a northeasterly direction along the White Slough before turning east as it crosses over State Route 29 and heads to its eastern terminus at I-80 as the James Capoot Memorial Highway (honoring a Vallejo police officer who was killed in the line of duty).

[14] As a result of the State Highways Acts of the early 20th century, the Black Point Cut-off was built over it and opened to traffic in 1917.

[22][23] House Representative Richard J. Welch was one of the earliest government officials to pressure the State of California to acquire the toll road in order to convert it into a toll-free highway.

[24] A Navy Department deed permitting the State to purchase the road was granted by the Attorney General on October 26, 1938.

However, opposition from residents in surrounding neighborhoods as well as a federal oil embargo only allowed widening of the approach between Fairgrounds Drive and I-80.

In 1977, a levee broke and flooded a portion of the developed land, turning it into protected wetlands that is home to endangered species.

The section between Sears Point and Mare Island was plagued with fatal accidents, earning its nickname of "Blood Alley".

In a preliminary effort to reduce the fatalities, officials established both a daylight test section, requiring all cars to keep their headlights on during the day, and passing lanes.

[26] In 1993, local resident Jim Poulos campaigned to have a barrier erected after the death of his 18-year-old son, Frankie, on "Blood Alley".

At first, Caltrans thought the barrier would make matters worse since it would be difficult for emergency vehicles to attend to accidents; environmental issues were also cited.

To alleviate this problem, Caltrans implemented electric gate technology, which would allow emergency vehicles to cut through certain parts of the median.

As a result, crews placed timbers and sheeting to protect foliage, and added holes into the median barrier to allow the mice to cross the highway.

[28] After environmental studies on the White Slough, Caltrans widened and elevated that section of the road and converted it to a freeway.

[31] On the morning of Friday February 15, 2019, the westernmost portion of the westbound highway (between Atherton Ave. and U.S. Route 101) was closed due to flooding caused by a levee break.

[35] In 2017, it was estimated that it would cost $4 billion to fix all the flooding, traffic, and other issues along the corridor, and based on transportation funding levels it would take until 2088 to come up with that amount of money.

[36][31] In 2022, California State Senator Bill Dodd introduced new legislation that would make the route a toll road again between Sears Point and at least Mare Island.

[38] In May 2023, the California Transportation Commission unanimously approved a plan to toll both directions, as well as widen the highway from a two-lane road to one with carpool lanes by converting the existing shoulders.

[39] Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage.