Webpack React Default URL - reactjs

Question

I am trying to figure out how to set the config up to by default load a different url as the base. Currently it is loading localhost:3000 - I need it to load localhost:3000/market. Client doesn't want the base path to work. For example if this was google, http://google.com wouldn't work and only http://google.com/market would.
I have checked quite a few stacks and this React with webpack was the closest I could find, however I can't use flags for the different environments, so I need it in the config, and I cannot for the life of me figure that out.
This is what I have in my webpack so far:
const appConfig = {
version: pkg.version,
basePath: process.env.BASE_URL,
api: {
baseUrl: `${process.env.BASE_URL}/api`,
},
auth: {
name: "ping",
config: {
clientId: process.env.CLIENT_ID,
authorizationUri: "redacted",
scopes: process.env.SCOPES,
},
},
};
module.exports = {
entry: './src/index.tsx',
output: {
path: path.join(__dirname, 'build/'),
filename: 'marketplace2.js',
globalObject: 'this',
publicPath: '/',
},
mode: nodeEnv,
resolve: {
plugins: [newTsConfigPathsPlugin],
extensions: ['.tsx', '.ts', '.js'],
},
target: 'web',
devServer: {
static: path.join(__dirname, './src'),
open: true,
port: 3000,
},
module: {
rules: [
{
test: /\.(js|jsx|json)$/,
exclude: /node_modules/,
use: ['babel-loader'],
},
{
test: /\.(ts|tsx)$/,
exclude: /node_modules/,
use: ['ts-loader'],
},
{
test: /\.(css|scss)$/,
use: ['style-loader', 'css-loader', 'sass-loader'],
},
{
test: /\.(jpg|jpeg|png|gif|mp3|svg|webp|ico)$/,
exclude: /node_modules/,
use: ['file-loader?name=[name].[ext]'],
},
],
},
plugins: [
new HtmlWebpackPlugin({
template: path.join(__dirname, './public', 'index.html'),
favicon: path.join(__dirname, './public', 'favicon.ico'),
manifest: path.join(__dirname, './public', 'manifest.json'),
}),
new Dotenv(),
new webpack.DefinePlugin({
"process.env.NODE_ENV": JSON.stringify(nodeEnv),
"process.env.SERVER": "false",
"process.env.RUN_CONFIG": JSON.stringify(appConfig),
}),
new CopyWebpackPlugin({
patterns: [
{ from: 'public', to: 'public' },
]
}),
],
};