Physician-assisted suicide in the United States is legal in:
Oregon (1994), Washington (2008), Vermont (2013), California (2015), Colorado (2016), Washington, D.C. (2017), Hawaii (2018)
In Montana, the Baxter v. Montana (2009) court decision created a defense for a physician who is prosecuted should the physician be charged in assisting a suicide, although prosecutions and convictions for assisted suicide remain possible in Montana.
Since Oregon legalized assisted suicide in 1994, many states have rejected assisted-suicide measures, some multiple times. Since January 1994, there have been more than 200 legislative proposals in more than 35 states. 
2018 Physician-Assisted Suicide State Legislation
All efforts to legalize and regulate physician-assisted suicide via state legislation failed in 2018, with the exception of Hawaii. The following list details the bill numbers for proposed legislation in favor of physician-assisted suicide in each state during 2018 legislative sessions.
||SB 2727 (Adopted)
||A 1504, S 1072