While 'essential' public services such as police and fire protection a
re provided in virtually every city,'optional' public services, such a
s museums or stadiums, are often found in larger cities. By using a si
mplified;urban land use theory model, this paper examines why optional
public services are offered and why cities organize to jointly provid
e these services. Results suggest that optional public services are pr
ovided when their cost is 'small' relative to the cost of essential pu
blic services. An expansion of the model suggests that when optional p
ublic services are jointly provided, cities vary in size as model para
meters vary.