Anyone know the laws regarding districts for cities?

[Sorenroy]

I do not remember where, but I seem to recall reading that once a city reaches 100,000 people it must adopt districts for electing city council members. Seeing as I live in a city that will likely surpass that number on the 2020 census, can anyone confirm or deny this? Sources/links would be very helpful.

Edit: I figure it would be helpful to mention that I live in Asheville, NC as there are probably very different laws from state to state.

[True Federalist (진정한 연방 주의자)]

If there is a State with such a provision it isn't North Carolina. Until either State or city laws are changed, Asheville will have six at-large council members and an elected mayor, regardless of it's size.

The relevant North Carolina laws are:

G.S. § 160A-66.  Composition of council.
Unless  otherwise  provided  by  its  charter,  each  city  shall  be  governed  by  a  mayor  and  a
council  of  three  members,  who  shall  be  elected  from  the  city  at  large  for  terms  of  two  years

and:

G.S. § 160A-101.  Optional forms.
Any  city  may  change  its  name  or  alter  its  form  of  government  by  adopting  any  one  or combination of the options prescribed by this section:
[...]
(4) Terms of office of members of the council:
Members of the council shall serve terms of office of either two or four years.  All  of  the  terms  need  not  be  of  the  same  length,  and  all  of  the  terms need not expire in the same year.

(5) Number of members of the council:
The council shall  consist of  any number of members not less than three nor more than twelve.

(6) Mode of election of the council:
a. All  candidates  shall  be  nominated  and  elected  by all the  qualified voters of the city.

b. The  city  shall  be  divided  into  single-member  electoral  districts; council  members  shall  be  apportioned  to the districts so that each member represents the same number of persons as nearly as possible, except  for  members  apportioned  to  the  city  at  large,  if  any;  the qualified  voters  of  each  district  shall  nominate  and  elect  candidates who reside in the district for seats apportioned to that district; and all the  qualified  voters  of  the  city  shall  nominate  and  elect  candidates apportioned to the city at large, if any.

c. The  city  shall  be  divided  into  single-member  electoral  districts; council  members  shall  be  apportioned  to  the  districts  so  that  each member represents the same number of persons as nearly as possible, except  for  members  apportioned  to  the  city  at  large;  and  candidates shall   reside   in   and   represent   the   districts   according   to   the apportionment  plan  adopted,  but  all  candidates  shall  be  nominated and elected by all the qualified voters of the city.

d. The  city shall  be  divided  into  electoral  districts  equal  in  number  to one  half  the  number  of  council  seats;  the  council  seats  shall  be divided  equally  into  "ward  seats"  and  "at-large  seats,"  one  each  of which  shall  be  apportioned  to  each  district,  so  that  each  council member represents the same number of persons as nearly as possible; the   qualified   voters   of   each   district   shall   nominate   and   elect candidates  to  the  "ward  seats";  candidates  for  the  "at-large  seats" shall   reside   in   and   represent   the   districts   according to   the apportionment  plan  adopted,  but  all  candidates  for  "at-large"  seats shall be nominated and elected by all the qualified voters of the city.

e. The  city  shall  be  divided  into  single-member  electoral  districts; council  members  shall  be  apportioned  to the  districts  so  that  each member represents the same number of persons as nearly as possible, except  for  members  apportioned  to  the  city  at  large,  if  any;  in  a nonpartisan   primary,   the   qualified   voters   of   each   district   shall nominate two candidates who reside in the district, and the qualified voters  of  the  entire  city  shall nominate  two  candidates  for  each  seat apportioned  to  the  city  at  large,  if  any;  and  all  candidates  shall  be elected by all the qualified voters of the city.

If either of options b, c, d or e is adopted, the council shall divide the city into  the  requisite  number  of  single-member  electoral  districts  according  to the apportionment plan adopted, and shall cause a map of the districts so laid out to be drawn up and filed as provided by G.S. 160A-22 and 160A-23. No more than one half of the council may be apportioned to the city at large. An initiative   petition   may   specify   the   number   of   single-member   electoral districts   to   be   laid   out,   but   the   drawing   of   district   boundaries   and apportionment of  members  to  the  districts  shall  be  done  in  all  cases  by  the council.

(7) Elections:
a. Partisan. – Municipal primaries and elections shall be conducted on a partisan basis as provided in G.S. 163-291.

b. Nonpartisan  Plurality. – Municipal  elections  shall  be  conducted  as provided in G.S. 163-292.

c. Nonpartisan Election and Runoff Election. – Municipal elections and runoff elections shall be conducted as provided in G.S. 163-293.

d. Nonpartisan   Primary   and   Election. – Municipal   primaries   and elections shall be conducted as provided in G.S. 163-294.

(8) Selection of mayor:
a. The mayor shall be elected by all the qualified voters of the city for a term of not less than two years nor more than four years.

b. The   mayor   shall   be   selected   by   the   council   from   among   its membership to serve at its pleasure.

Under option a, the mayor may be  given the right to vote on all matters before the council, or he may be limited to voting only to break a tie. Under option b, the mayor has the right to vote on all matters before the council. In both  cases  the  mayor   has  no  right  to  break  a  tie  vote  in  which   he participated.
[...]

From Asheville's charter:

Sec. 6. - Composition; qualifications and terms of members.

Except as otherwise herein provided in this Charter, all powers of the city shall be vested in a council of a mayor and six councilmembers, all nominated and elected from the city at large in the manner hereinafter provided. The mayor and members of the council, and all other officers, elected under the provisions of this Charter, shall at the time of their election be qualified electors of the City of Asheville. The term of the mayor and councilmembers shall begin at the first regular meeting of the city council next following their election as set forth hereinafter. The term of office of the mayor and six councilmembers shall be four years, and shall be so staggered that the terms of office of three councilmembers shall expire every two years. Said staggered terms shall begin following the election of 1997, with those three persons elected to council who receive the highest number of votes of the entire council to serve four year terms to expire in 2001, and the other three persons elected to council to serve two year terms to expire in 1999. Commencing with the 1999 election, all terms of office for council members shall be four years. The person elected as mayor at the 1997 election shall serve a four year term of office commencing in 1997 and expiring in 2001. Thereafter, all terms of office for the mayor shall be four years. A mayor or member of council ceasing to possess any of the qualifications specified in this section shall immediately forfeit office.

[Kushahontas]

Austin only adopted council districts in the last municipal election, and it already had around 800k people in it. Columbus only recently adopted such a system with a similar population, as well.

[Torie]

The only law of general application that I know about is the VRA. If at large voting effective precludes minorities electing candidates of their choice in individual districts, then there is a problem. If it were ever adopted, at large voting might well turn out to be illegal in my own city of Hudson, tiny as it is, because it's about 25% black.

[publicunofficial]

Seattle only recently switched from at-large council seats to district-based seats, and it was only through a citizen's referendum.

[BuckeyeNut]

Not a (national) thing. Columbus' population is nearing a million and all seven council members are elected at-large.

EDIT: Though, IIRC, Columbus is the largest city without council wards.