Family members, elected officials and other leaders will gather in Newtown on Friday for a day of remembrance and a call to action. The reading of names is expected to take 12 hours.
Mayors Against Illegal Guns will launch a bus tour that will travel to 25 states over 100 days to build support for background checks legislation. Legislation to expand background checks for gun buyers failed in the Senate in April.
The mayors group is also holding events in 10 states calling for lawmakers to expand background checks and urging senators who opposed the bill to reconsider. Those events, which include gun violence survivors and gun owners, will be held in Arkansas, Arizona, Florida, Georgia, Indiana, Montana, North Carolina, New Hampshire, Ohio and Pennsylvania.
The gunman in Newtown killed his mother and then 20 children and six adults at Sandy Hook Elementary School on Dec. 14 before committing suicide as police arrived.
Some of the victims' families are in Washington this week lobbying lawmakers for action.
New York Mayor Michael Bloomberg, who co-founded the mayor's group, this week sent a letter asking donors not to support Democratic senators who opposed the bill to expand background checks.
On the other side of the debate, the National Rifle Association is focusing on Sen. Joe Manchin, D-W.Va., who co-sponsored the bill to expand background checks, with a TV ad urging viewers to phone Manchin's office and tell him "to honor his commitment to the 2nd Amendment." The NRA plans to spend $100,000 airing the ad in West Virginia markets over the next two weeks.