A Colorado inmate's lawsuit is among a string of court cases in the U.S. involving the treatment of transgender inmates in state and federal prisons. Advocates count a number of landmark policy changes and rulings in recent years. Here's a look at some of them:

1994: The U.S. Supreme Court rules that a transgender woman who was assaulted while in federal prison could seek damages against prison officials.

2003: The Prison Rape Elimination Act is signed into law. The sweeping law requires that prisons make decisions about where to house transgender people on a case-by-case basis, rather than going by genital characteristics or gender at birth.

2011: A settlement with a transgender woman seeking treatment for gender identity disorder prompts the Federal Bureau of Prisons to end its "freeze-frame" policy of only providing treatment that the inmate was receiving when entering prison.

2011: A federal appeals court strikes down a Wisconsin law barring hormone therapy or sex reassignment surgery while an inmate is in state custody.

2015: San Francisco officials announce the city's jail will house transgender inmates based on their gender identity.

2017: A transgender woman serving a life sentence for murder in California becomes the first U.S. inmate to receive state-funded sex-reassignment surgery.

2017: A transgender woman named Passion Star reaches a settlement with Texas that requires changes to the prisons' intake process and makes it easier for LGBT inmates to get into "safekeeping" areas in prisons. Star reported multiple assaults and rapes while she was incarcerated.

2018: New York City jails announce transgender inmates will be housed with fellow inmates of the gender with which they identify.

2018: A Missouri District Court judge rules that the state corrections agency cannot bar an inmate's access to hormone therapy because he or she was not receiving treatment before being jailed.