Migrating CSV Data - Drupal 8.5.3

Building Address Project
 
Given a CSV file and a matching content type, here's how we get the data migrated into Drupal.
The following modules will be required:
Migrate, Migrate Plus, Migrate Source CSV, Migrate Tools, Migrate Drupal UI
 
Note that in this example we will import latitude, longitude into a geofield.
 
I had some drush migrate-import errors and needed to work with composer to get he latest dev version installed for Migrate Tools.
 
drush migrate-import mailstops_import
drush migrate-rollback mailstops_import
  
This one was helpful for removing broken migrations I had created along the way:
drush config-delete
 
* Create a migration group at /admin/structure/migrate
* Create the CSV file
    * The CSV will need a column inserted for 'id'. This can be a unique number created via Excel.
    * The quoting of some or all data may be required. Note that you'll need to specify delimiter and quoting in the YAML file
* Create the YAML file
    * To get a head start, go to /admin/config/development/configuration/single/export
    * Select Migration and the migration you just created in step 1
    * Copy the outline into a text editor and modify it. This is the step where you'll end up needing to do research if you're importing geofield or location data to understand if you are relying on a plugin.
 
Sample YAML 
uuid: 0a672ec8-3f52-42e3-a1db-eaab8c7f26ba
langcode: en
status: true
dependencies: {  }
id: mailstops_import
class: null
field_plugin_method: null
cck_plugin_method: null
migration_tags: null
migration_group: null
label: 'Import Mailstops'
source:
  plugin: csv
  path: /var/www/html/mailstops.csv
  delimiter: ','
  enclosure: ''
  header_row_count: 1
  keys:
    - id
  column_names:
    -
      id: id
    -
      title: title
    -
      address: address
    -
      room: room
    -
      city: city
    -
      state: state
    -
      zip: zip
    -
      latitude: latitude
    -
      longitude: longitude
process:
  title: title
  field_address: address
  field_room: room
  field_city: city
  field_state: state
  field_zip: zip
  field_location:
    plugin: geofield_latlon
    source:
      field_location/lat: latitude
      field_location/long: longitude
  type:
    plugin: default_value
    default_value: mailstop
destination:
  plugin: 'entity:node'
migration_dependencies: null
 
Sample CSV
id,title,address,room,city,state,zip,latitude,longitude
1,ACADEMIC PERSONNEL OFFICE,500 Kerr Road,499,Santa Cruz,California,95064,36.9954,-122.061
2,ACADEMIC SENATE,500 Kerr Road,125,Santa Cruz,California,95064,36.9954,-122.061
3,ACCOUNTING OFFICE,2300 Delaware Ave.,Suite A208 A212,Santa Cruz,California,95064,36.9563,-122.059
4,ACE PROGRAM,606 Engineering Loop,199,Santa Cruz,California,95064,37.0002,-122.063