[2] She was previously a member of the California State Assembly (1996–2002), where she became the first freshman, first woman, and first lesbian to chair the Committee on Appropriations.

As a member of the State Assembly, Migden authored legislation to create California's domestic partner registry, promote children's health, preserve the old growth Headwaters Forest, increase accountability in K–12 schools, protect borrowers from predatory and deceptive lending practices, protect consumers from manipulation by energy generators, and promote the use of emergency contraception.

[3][4] In 1998, Migden authored the '‘Safe Needles Act'’ (AB1208 - 1998) that became a national model for legislation that President Clinton signed into law in 2000.

Migden authored the '‘Clean Water Act'’ in 1999 that imposed tougher penalties on industrial polluters dumping harmful toxins in California waterways.

[5] Over the last seven years Migden has authored legislation for domestic partnership in California providing benefits to the LGBT community and unmarried senior citizens.

Assembly Bill 26 in 1999 marked the first time in the nation a state legislature passed a domestic partnership statute without forcible intervention of the courts.

[15] In 2002 Migden authored legislation (AB 1860) requiring the state to provide information regarding the "morning after" contraception to female victims of sexual assault.

Migden's third bill passed and resulted in cutting the amount of surplus funds the county will annually pay to the state by half.

[23] Migden underwent rigorous and difficult chemotherapies for two years before finally becoming a participant in clinical trial, which ultimately got FDA approval for Gleevec,[24] which has proven to be a watershed cancer drug.

In 1996, Migden ran a stop sign by the State Capitol and crashed into a 1990 Dodge Spirit sedan owned by Teresa Latham.

On May 18, 2007, Migden crashed her SUV into a sedan which was stopped at a red light, injuring Ellen Butawan and her 3-year-old daughter, who were sent to the emergency room.

Migden claimed that her "wild ride" occurred during state business, so that the Department of General Services paid $335,000 to Butawan in July 2009.

"[23] On August 10, 2007, Migden entered a nolo contendere (no contest) plea to charges of reckless driving, paid a $710 fine and was sentenced to two years of probation.

[31] In 1998 Migden was named "Rookie of the year" award by the California Journal, giving her top honors in the categories of integrity, intelligence, hardest working and most influential.

Seeking a second term in the state senate, Migden failed to win renomination in the 2008 primary election held on 2008-06-03.