NASFiC, the North American Science Fiction Convention was added to the Worldcon Constitution in the mid 1970s. It was intended to legitimatize the inevitable major convention in North America when the Worldcon was held in other parts of the world without encouraging the development of an American natcon, which would inevitably become a competitor to Worldcon.

The first NASFiC was held in Los Angeles in 1975 when the first Aussiecon was in Melbourne, Victoria, Australia. The second NASFiC (NorthAmericon) was in Louisville, Kentucky in 1979 when Brighton, England was selected for the Worldcon. The name "NASFiC" was coined by Tony Lewis.

1 - NASFiC (first) - Labor Day weekend 1975, Los Angeles, California. Los Angeles Airport Marriott.
Guest of Honor: Harlan Ellison. Chairman: Chuck Crayne. Attendees: 1,100.

2 - NorthAmericon `79 - 30 Aug-3 Sep 1979 Louisville, Kentucky Galt House Hotel
Guests of Honor: Frederik Pohl (pro), George Scithers (fan). Chairman: Cliff Amos. Attendees: 1928/2030

3 - LoneStarCon - 30 Aug - 2 Sep 1985, Austin,Texas, Hyatt Regency Austin, Sheraton Crest & Palmer Auditorium
Guests of Honor: Jack Vance (writer), Richard Powers (artist), Joanne Burger (fan). Chairman: Willie Siros. Attendees: 2,800

4 - CactusCon, 3-7 Sep 1987, Phoenix, Arizona. Phoenix Hyatt Regency, Adams Hilton, Phoenix Convention Center
Guests of Honor: Hal Clement (pro), Marjii Ellers (fan). Chairman: Bruce Farr. Attendees: 3000

5 - ConDiego, Labor Day weekend 1990, San Diego, California Omni Hotel, San Diego Convention & Performing Arts Center
Guests of Honor: Samuel R. Delany (pro), Ben Yalow (fan). Chairman: Albert Lafreniere II. Attendees: 3000

6 - Dragon*Con 1995, 13-16 July 1995 Atlanta, Georgia. Atlanta Hilton & Towers, Westin Peachtree Plaza Hotel & Atlanta Civic Center
Guests of Honor: George Alec Effinger (writer), Harlan Ellison (writer), Timothy Zahn (writer), Michael Whelan (artist), Bjo Trimble (fan). Chairman: Ed Kramer. Attendees: 14,312

7 - Conucopia, 26-29 Aug 1999 Anaheim, California. Anaheim Marriott
Guests of Honor: Jerry Pournelle (pro), Ellen Datlow (editor), Richard Lynch (fan), Nicki Lynch (fan). Chairman: Christian B. McGuire. Attendees: 1,734

8 - CascadiaCon, 1-5 Sep 2005 Seattle, Washington.
Guests of Honor: Fred Saberhagen (Writer), Liz Danforth (Artist), Toni Weisskopf (Editor), Kevin Standlee (Fan). Chairman: Bobbie DuFault. Attendees: 1785/2014

9 - Archon 31/Tuckercon, 2-5 Aug 2007, Collinsville, Illinois. Holiday Inn Gateway Center
Guests of Honor: Barbara Hambly (Featured), Darrell K. Sweet (Artist), Kevin Murphy & Bill Corbett (Media), James Ernest (Gaming), Elizabeth Covey (Costuming), Barry & Sally Childs-Helton (Filk), Nancy "Cleo" Hathaway (Fan), Lani Tupu (Media/Workshop), Richard Hatch (Last-Minute Special). Chairmen: Steve Norris, Michelle Zellich. Attendees: ????

10 - Reconstruction, 5-8 Aug 2010, Raleigh, NC. Raleigh Convention Center, Raleigh Marriott City Center & Sheraton Raleigh Hotel.
Guests of Honor: Eric Flint, Brad Foster (Artist), Juanita Coulson (Fan). Chairman: Warren Buff. Attendees: ????

11 - Detcon1, 17-20 Jul 2014, Detroit, MI. Renaissance Center Marriott, Detroit.
Guests of Honor: Steven Barnes, John Picacio, Bernadette Bosky, Arthur D. Hlavaty, Kevin J. Maroney, Helen Greiner, Bill Sutton, and Brenda Sutton. Chairman: Tammy Coxen. Chairs Emeritus: Roger Sims and Fred Prophet.

12 - NOrthAmeriCon '17, July 6-9, 2017, San Juan, PR. Sheraton Puerto Rico Hotel and Casino, Puerto Rico, PR.
Guests of Honor: DaĆ­na Chaviano, Tobias S. Buckell, Guy Consolmagno, Javier Grillo-Marxuach, George Perez, Paula Smith

13 - Westercon 72, July 4-7, 2019, Layton, UT. GoH Jim Butcher, Vincent Villafranca, Kitty Krell, Kevin Standlee, Lisa Hayes & Kuma Bear

See also Noncon (fanspeak); the major difference being that the location of the NASFiC is determined by members of the Worldcon.