When she opened for business more three decades ago, Martha Howard was unsure if the town of Inverness could support a law firm. But her small-town sensibilities led to enduring relationships with her clients and helped spur the growth of her firm, which has managed wills and other forms of trusts for homeowners across West Marin and the Bay Area since 1980.

“You get known for the way you operate in a community”—especially one as sparsely populated as West Marin, said Ms. Howard, whose business relies mainly on word of mouth.

With a degree from the University of California’s Hastings College of the Law, Ms. Howard has developed a reputation for her ability to navigate an evolving tax system that, after years of uncertainty, is starting to show signs of consistency.

She sees her role in West Marin as a way to help “unravel” her clients’ assets into trusts and wills, at times involving a “cumbersome process” of developing relationships between beneficiaries, typically family members and relatives of the guarantor.

Ms. Howard lives only a few blocks from her office, but she is known to visit the homes of elderly and disabled clients. That was how she met Dino Williams, whose mother, at the time in a wheelchair, struggled to make appointments at the firm as she was organizing her will.

In the late 1990s Ms. Howard offered an administrative position to Ms. Williams, who was seeking part-time work.

An administrator for the National Park Service for about 30 years, Ms. Williams, who is a notary public, has found satisfaction in a role at the law firm she said helps people “get their affairs in order.”

The firm expanded its staff about two weeks ago, when Ms. Howard hired Dakota Whitney, who specialized in contractual litigation at a San Francisco law firm for about seven years after earning a law degree from Hastings.

Ms. Whitney traces her lineage to Oscar Shafter, a lawyer on the state Supreme Court who purchased the Point Reyes peninsula with his brother, James, in the mid-1880’s.

Her dreams of working as a small-town lawyer began taking shape a couple of years ago during conversations with Ms. Howard. “I’ve always known about her,” she said of Ms. Howard, whom she described as having a reputation for her “human connection with her clients.”

Although the recent hire has led some to speculate about her retirement, Ms. Howard assured she intends to remain a part of the law firm. “I don’t want to retire,” she said, “not for a really long time.”